Non-ablative multi-layer coatings that prevent water-derived damage, corrosion, and deterioration from biological chemical processes

ABSTRACT

Methods of protecting a surface include applying an inner polymer layer onto a surface. The inner polymer layer is impregnated with a biologically active chemical substance that protects the surface from biofouling-induced chemical, biological, and bio-proliferative damage. The inner polymer layer is an epoxy polymer. An outer polymer layer is applied onto the inner polymer layer. The outer polymer layer is impregnated with a biologically active chemical substance that protects the inner polymer layer from biofouling-induced chemical, biological, and bio-proliferative damage. The outer polymer layer is selected from the group consisting of polyurethanes and fluorourethanes.

BACKGROUND OF THE INVENTION

The present invention relates to protective coatings for surfaces submerged in water, and, more particularly, to multi-layer coatings having layers that include chemicals to nullify deterioration from chemical and biological factors in the water.

Structures that are submerged within water, whether saltwater or freshwater, are subject to attack by chemical, galvanic, corrosive, ultraviolet, mechanical, and bio-proliferative processes that cause deterioration, damage, and eventual destruction of the surface of the submerged object. If that submerged object is coated with a protective coating to prevent such damage to the structure, such deterioration can be delayed. However, the coating itself is subject to the same attack of these processes, and thus the protection provided by the coating is only temporary. Eventually, both the coating and the submerged structure fail and are destroyed. To prevent this, the damaged coating may be periodically removed and replaced before structural damage has occurred. In almost all cases, materials related to the coating are released into the aquatic environment, which may have an undesirable effect on the water and life forms in the surrounding water.

BRIEF SUMMARY OF THE INVENTION

A method of protecting a submerged surface or a surface to be submerged in water include applying an inner polymer layer onto a surface. The inner polymer layer is impregnated with a biologically active chemical substance that protects the surface from biofouling-induced chemical, biological, and bio-proliferative damage. The inner polymer layer is an epoxy polymer. An outer polymer layer is applied onto the inner polymer layer. The outer polymer layer is impregnated with a biologically active chemical substance that protects the inner polymer layer from biofouling-induced chemical, biological, and bio-proliferative damage. The outer polymer layer is selected from the group consisting of polyurethanes and fluorourethanes.

A method of protecting a submerged surface or a surface to be submerged in water includes applying a non-ablative inner polymer layer onto a submerged surface or a surface to be submerged in water. The inner polymer layer is impregnated with a biologically active chemical substance that protects the surface from biofouling-induced chemical, biological, and bio-proliferative damage. The inner polymer layer is a flexible epoxy polymer. A non-ablative outer polymer layer is applied onto the inner polymer layer. The outer polymer layer is impregnated with a biologically active chemical substance that protects the inner polymer layer from biofouling-induced chemical, biological, and bio-proliferative damage by synergistic simultaneous repulsive effects on the octopamine, GABA, and TRPV1 cell membrane receptors of biofouling animal organisms. The outer polymer layer is selected from the group consisting of polyurethanes and fluorourethanes.

A method of protecting a submerged surface or a surface to be submerged in water includes applying a non-ablative inner polymer layer onto a submerged surface or a surface to be submerged in water. The inner polymer layer is impregnated with a biologically active chemical substance that protects the surface from biofouling-induced chemical, biological, and bio-proliferative damage. The inner polymer layer is a flexible epoxy polymer. A non-ablative outer polymer layer is applied onto the inner polymer layer. The outer polymer layer is impregnated with a powdered copper-zinc-tin alloy that remains chemically intact in contact with the surrounding water. The outer polymer layer is selected from the group consisting of polyurethanes and fluorourethanes.

These and other features and advantages will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will provide details in the following description of preferred embodiments with reference to the following figures wherein:

FIG. 1 is a diagram illustrating a cross-sectional view of a multi-layer coating that inhibits the attachment and growth of bio-proliferative organisms, thereby protecting an underlying surface from damage, in accordance with an embodiment of the present invention; and

FIG. 2 is a diagram illustrating a life cycle of bio-proliferative organisms, including illustration of how such organisms may be inhibited from attaching to a surface, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

Coatings may be provided for submerged structures that protect the structure for a significant length of time, without shedding of material into the environment. Two or more layers of polymers may be used, each impregnated with different chemical compounds that performs different respective purposes, preventing the attachment of biofouling animal and plant organisms and related bio-proliferative processes, such as scale and shell formation.

For example, an outer polymer layer may prevent the settlement of larval biofouling animal organisms, repelling them from the surface of the coating. For the very small minority of remaining biofouling animal organisms that manage to attach to and penetrate the outer polymer layer, these organisms may contact an inner polymer layer. The inner polymer layer may include chemical substances that eliminate the organisms. Because the inner polymer layer is enclosed within the outer polymer layer, no chemicals from the inner layer leech into the surrounding water. The layers may not be ablative in nature, so that neither the chemical components of the polymers comprising the layers, nor the chemical substances impregnated into the layers, are released into the environment.

Referring to FIG. 1 , a multi-layer coating for a structure is shown. An outer polymer layer 98 covers an inner polymer layer 99. The outer polymer layer 98 prevents deterioration, corrosion, and damage to the inner polymer layer 99 by preventing physical interactions, such as diffusion, solution, or any chemical interaction between the surrounding water and any of the inner polymer layer's constituents. For example, a surrounding medium, such as water 106, may include Cl− ions, CO₃-3 ions, H+ ions, or SO₄-2 ions.

Because of the shielding effect of the outer polymer layer 98 over the inner polymer layer 99, the aquatic environment and water 106 surrounding the coating and protected surface 105 is prevented from contacting the inner polymer layer 99. As a result, no chemical species, including ions or complete molecules, that are related to any of the structural or chemical components of the inner polymer layer 99 would be found at any measurable distance away from the submerged surface 105 being protected. As a further result, even water soluble substances, such as cupro-metallic salts, will not dissolve into or leach or diffuse away from the protected surface coating for any significant distance. For example, such substances may include CuSO₄, CuNO₃, copper thiosulfate, or any water soluble salt that contains cuprous Cu+1 or cupric Cu+2 ions, cupric acetate, any other water soluble salt containing metallic cations and non-metallic anions.

Preventing contact between water 106 and the inner polymer layer 99 helps to preserve the integrity of the surrounding aquatic environment. An optional outer primer 103 between the inner polymer layer 99 and outer polymer layer 98 increases the containment of chemical materials within the inner polymer layer 99, and may itself be impregnated with chemical materials that will slow the proliferation of the juvenile animal organisms that have developed from larvae that have successfully managed to settle on the outside polymer layer 98. An optional inner primer layer 104 can also be used to increase adhesion of the coating to the protective surface structure and to prevent galvanic activity between a metal surface structure and the chemical substances in the inner polymer layer 99.

Various processes can attack coatings and their protected surfaces. Such processes may include chemical processes; galvanic corrosive processes; radiant processes of ultraviolet light transmission from the atmosphere through the water to ultraviolet-sensitive coatings; mechanical processes such as friction with moving objects in the water or the abrasive friction of the water itself, collision with fish and other animals, or hard docking into a pier; and bio-proliferative processes involving the growth of animal and plant organisms on the protected surfaces and their coatings. Any of these processes can act predominantly alone, or in combination, to first damage and destroy a protective coating, and then sequentially the protective surface structure itself. Of note, bio-proliferative processes have special significance if they are uncontrolled, as they will lead to secondary chemical, galvanic, and corrosive processes, independent of what originates from the properties of the water surrounding the protected surface structure.

Chemical processes may include chloride ion attack on stainless steel, scale precipitation of calcium and magnesium carbonate and sulfate on both the coatings and exposed structural surfaces, hydrogen and sulfide ion attack on metal surfaces, and oxygen attack on ferric surfaces resulting in rust.

Galvanic corrosive processes may include electron transfer between dissimilar metals on a boat and electrical leakage currents in the water surrounding the surface.

Bio-proliferative processes may involve the proliferation of biological substances, with or without the involvement of discrete biological organisms, such as biofouling observed with barnacles, invasive mussels, tubeworms, ship worms, tunicates, algae, bacteria, fungi, and other organisms. Bio-proliferative processes may also include scale formation without the actual presence of living organisms.

Bio-proliferative processes can be inhibited by the inclusion of various compounds in the coating. At one time, a group of similarly structurally related chemical compounds, known as tri-butyl-tins (TBT), was used to eradicate bio-proliferative processes that included biofouling. However, TBT was found to be highly toxic, because, to eradicate the various types of biofouling that can occur, TBT had to be released into the surrounding water by the reaction and dissolution of the paint coating that was impregnated by the compound. As a result significant numbers of aquatic organisms suffered harm. In 2003, however, the International Maritime Organization (IMO) issued a permanent ban which forbade the use of TBT.

With this ban, TBT was largely supplanted by copper salts in ablative paints that reacted with the surrounding salt water to produce copper compounds, such as copper hydroxy-chloride that also eradicated bio-proliferation in the same manner as TBT. Now, many jurisdictions are considering banning copper ablative paints for the same reason that TBT was banned.

To prevent exposure of the aquatic environment to potentially harmful chemicals, the present coatings make use of a multi-layer structure, whereby potentially toxic materials are safely enclosed within the outer polymer layer 98. The outer polymer layer 98 uses safer inhibitory chemicals to prevent bio-proliferative organisms from attaching, while the inner polymer layer 99 selectively exposes organisms to more toxic chemicals when those organisms manage to penetrate the outer polymer layer 98.

Not only does the coated structure need to be protected from water-derived destructive processes, but the coating itself needs to be protected. Each layer of the coating protects the layer underneath it. Because the multi-layer structure makes it possible to segregate chemicals from exposure to the water 106, a wide array of chemicals can be used, including those which are water soluble or which would be harmful to the environment if exposed to the water directly. To effectively provide protection for the surface 105, the layers of the coating are themselves designed to ensure their durability.

Thus, the outer polymer layer 98 may include environmentally friendly substances that repel biofouling animal organisms, thus protecting the underlying inner polymer layer 99 and the structure's surface 105. At the same time, the outer polymer layer 98 shields the aquatic environment from being in contact with the inner polymer layer 99, which may include substances that would kill biofouling animal organisms and could potentially be harmful to the surrounding aquatic environment. Exemplary substances that could safely be used in the inner polymer layer 99 include copper and its cupro-metallic salts, such as cuprous oxide, cupric oxide, copper sulfate, copper thiocyanate (both cuprous and cupric forms), and others.

Thus, the chemical materials described herein function to protect the coating itself and the underlying submerged surface structure. In achieving this objective, the present embodiments provide superior structural protection, and also eliminate the destructive, damaging, and deteriorating effects of the chemical, galvanic, corrosive, radiant (ultraviolet) and mechanical processes emanating from and within the surrounding water that damage the submerged surface structure subsequently.

In an illustrative embodiment, the outer polymer layer 98 may include a polymer 116 selected from the group of polyurethanes (PUR), fluorourethanes (FUR), polyurea polymers, and polyaspartate polymers as representative examples from the chemical class of compounds known as polymers. These polymers have mechanical, UV light—resistant optical, and curing qualities that make them well suited to provide initial protection for the coating and the inner polymer layer underneath from environmental damage. By protecting the inner polymer layer 99 from the radiant (UV), chemical, corrosive, and mechanical processes originating within and from the surrounding water, they are the first means of protecting the integrity of the entire coating and the submerged protected surface structure underneath.

Referring to PUR and FUR, these polymers have excellent optical and radiant resistance to ultraviolet light transmitted from the surrounding water. Thus, they can protect inner polymer layers that are UV sensitive and that would be prone to deterioration, such as epoxies, which can discolor and crack with time under UV exposure, a process known as caulking. PUR and FUR are mechanically ductile, very durable, and resistant to scratching and abrasion, and can handle a high degree of flexing forces. These features provide mechanical resistance against the mechanical processes of friction and impact. These properties also allow for self-sealing of microscopic defects that can occur with time in the coating. PUR and FUR are highly resistant to pitting because they resist the mechanical process of water vapor diffusion under the polymer, which can lead to condensation and bubble formation. PUR and FUR are highly adhesive to the underlying layer polymers such as epoxies. PUR and FUR are chemically inert to most acids, alkalis, the chloride ion, and all chemical species found in both saltwater and freshwater. The chloride ion is a major cause of chemical deterioration of surfaces and structures in seawater, and the hydrogen ion is the major problem in freshwater.

These chemical properties make PUR and FUR resistant to corrosive and galvanic processes that would damage the coating. Their extremely low coefficient of friction gives PUR and FUR resistance against the bio-proliferative processes of scaling attachment of calcium and magnesium carbonates and hydroxides attachment, both from the presence of scaling calcium forming biological organisms and from simple precipitation of salts from water saturated in these chemical species. However, those same extremely low coefficients of friction also increase the resistance of PUR and FUR to bio-proliferative processes such as biofouling, where organisms may attach and proliferate on the outer surface of the coating. The resistances provided by these polymers by itself are not sufficient to protect the coating against bio-proliferative processes associated with biofouling animal and plant organisms. While low friction can help to prevent attachment of organisms, for this characteristic to provide a significant benefit against such organisms, the boat should be moving at least 10 mph relative to the water to prevent settlement of biofouling animal and plant organisms.

To improve the bio-proliferative resistance of these polymers and to keep the integrity of the outer polymer layer 98 intact, the outer polymer layer 98 may be impregnated with certain chemical substances that inhibit attachment by organisms. Keeping the outer polymer layer 98 intact from damaging physical, bio-proliferative, and chemical processes from the surrounding water secondarily preserves the integrity of the inner polymer layer 99 from attack by these same damaging physical, bio-proliferative, and chemical processes, and the inner polymer layer 99 in turn protects the integrity of the submerged protected surface structure 105. Hence the polymer 116 of the outer polymer layer 98 is responsible for the initial step in the cascade of serial protections provided by the coating.

At the current time, because of cost and other considerations, FUR and PUR and especially FUR have not been widely adopted into immersive water applications of coatings, but have only been used primarily in surfaces subject to intermittent immersion and splashing, such as on shore coastal buildings or pylons of bridges. While PUR coatings can last 8 to 12 years if protected from bio-proliferative processes attacking such coatings, FUR coatings can last 25 to 60 years and perhaps as long as a century. FUR especially exhibits outstanding gloss and pigmentation color preservation after over 10 years of saltwater spray exposure.

To give the outer polymer layer 98 additional protection against bio-proliferative processes, such as biofouling animals and organisms, additional components may be added to that outer polymer layer 98 to prevent compromise of that layer's integrity. Without such additives, if a boat hull sits for a period of time in stagnant water, the lack of motion of the boat neutralizes the benefit of the low coefficient of friction property of the outer polymer layer that, in moving water, could prevent attachment of biofouling animal and plant organisms, and these entities will attach rapidly in great numbers to destroy the integrity of the outer polymer coating. Destroying the integrity of the outer polymer layer 98 rapidly will result in not only rapid demolishing of the integrity of the inner polymer layer 99 by not only bio-proliferative processes, but now the corrosive and chemical processes of the surrounding water will have access to the inner polymer layer 99, destroying its integrity as well. Then the integrity of the submerged surface structure will also then be compromised shortly afterwards. Thus, improving the resistance of the outer polymer layer 98 improves the durability of the entire coating.

A substance that may be added to the outer polymer layer 98 is a powdered alloy of copper, which may include copper, zinc, and tin particles 107, a family of alloys known commonly as the admiralty brasses. The polymer 116 may be impregnated with a water-insoluble and water-non-reactive brass powder 107, for example having particle size of 44 micron or smaller, modified with a doping of tin, to produce an admiralty brass alloy with a copper weight percentage of at least 85%, zinc with a weight percentage of at least 8%, and tin with a weight percentage of at least 1% and no more than 5%. One specific illustrative embodiment may have percentages that are about 90% copper, 9% zinc, and 1% tin.

The addition of tin, as compared to common brasses (e.g., 90% Cu, 10% Zn) gives the powder enhanced properties that make it suitable for inclusion in the outer polymer layer 98. This cupro-metallic alloy containing only small percentages of tin is classified as a type of admiralty brass known as a tin brass powder. The powder prevents corrosion of the outer layer 98 and, in consequence, the inner polymer layer 99 as well. This cupro-metallic alloy does this with the tin in the cupro-metal alloy powder preventing leaching of the zinc out of the alloy, a process known as dezincification. By preventing dezincification, the powder copper alloy particles 107 are prevented from breaking down into porous Cu particles, which disintegrate and release copper and copper ions into the surrounding water. Thus zinc prevents the environmental impact of including copper by preventing the copper from reaching the water. The tin doping further gives the cupro-metallic alloy a non-ablative property and allows it to remain intact chemically and mechanically upon exposure to seawater. With the inclusion of tin, this cupro-metallic alloy diminishes the presence of any galvanic action and corrosion initiated by the presence of the seawater. Additionally, if a compound such as zinc pyrithione is used in the outer layer 98, the presence of zinc in the alloy also helps keep the zinc pyrithione in the outer polymer layer 98 intact and prevents it from leaching out into the water if it were to dissolve into its constituent zinc and pyrithione ions.

Unlike the copper in pure copper metal or in copper salts widely used in ablative copper antifouling paints, the copper atoms in the tin-brass powder 107 is not released into the aquatic environment, because it is entrapped within the alloy complex as a solid metallic solution with metallic zinc by the action of the tin. The copper atoms are kept in their metallic state and are not changed into cupric or cuprous ions, which would otherwise leach into the surrounding water. The entrapment feature of the solid state alloy solution of the copper and zinc keeps the copper composition by weight constant over the extended life of the coating. The copper in the tin-brass alloy behaves differently from the copper in the cupro-metallic salts, or even pure copper powder or flakes that are found in ablative copper paints, whose copper atoms and cupric and cuprous ions leak profusely into the water on a continuous basis as the mechanism of their antifouling function. Finally, the inclusion of small amounts of metallic tin in the alloy improves the ability of the alloy powder and the outer polymer layer to repel biofouling animal larvae from the surface of the outer polymer layer. This alloy functions in this regard significantly better than cupro-nickel alloys, cupro-zinc brass alloys, and cupro-tin bronze alloys. However, if too much metallic tin is used, the retardation of bio-proliferative processes on the surface of the coating may actually be reduced.

The percentage of tin used by weight of the alloy mixture should not exceed 5%, with an optimal percentage being between 1% to 2%. The alloy employed in the outer polymer coating 98 by this invention may include 90% Cu, 9% Zn, and 1% Sn.

The alloy particles, which may be smaller than 44 microns and which may actually have a mean diameter of about 9 to about 14 microns, have a very large surface area to weight ratio, which improves its effectiveness. A composition of the alloy by weight of about 5% of the outer polymer layer is preferred, though a useable by weight concentration ranges from 1% to 20%. Note that if only 30% of the surface of outer layer 98 has tin brass particles exposed at the surface, because the anti-fouling influence of the alloy extends out a slight distance on the surface of the coating, the alloy powder will protect the entire surface. In contrast to the use of copper and other types of ablative paints, which shed the copper and other biocides into the water the biofouling inhibiting compounds may be used for protecting the coating and the protected surface from damage, disintegration, and discoloring. The elimination of biofouling organisms and the protection rendered to the coating and the surface below it is accomplished on the surface and upper portion of the multi-layered coating, with no chemically active substances being released into the surrounding water.

Referring now to FIG. 2 , an attachment process by cyprid larval forms of barnacles is shown. The tin brass alloy prevents bio-proliferative processes from being initiated by larval forms of biofouling animal organisms, such as the cyprid forms of barnacles and veliger forms of invasive mussels that touch the outer polymer surface. Cyprids and veligers may be about 2 mm in length. Using cyprids as examples, they manifest movement and behavior shown by four stages of attraction and repulsion: 117A—temporary attachment; 117B—using two “walking legs” head antennae 119, exploration; 117C—with exploration of the service for a suitable settlement spot, and if no such spot is found, 117D—repulsion from the surface. Cyprids move through the water using thoracic muscle structures 118.

The impregnated materials prevent the cyprids from finding a spot on the outer polymer coating that is suitable for settling and permanent attachment. First, the presence of copper atoms adjacent to the cell membrane area 125 of the larvae, being part of alloy particle 107, is disruptive to their cell membranes 125, thereby preventing settlement by this mechanism. Second, cyprids and veligers maneuver over the coating for some distance with their bodies and a pair of walking “legs” 119 in an attempt to settle on the coating, but they are repelled off the surface when these “legs” touch either an alloy particle itself 107 or a region of the coating close to the particle; the chemical influence of each copper zinc tin alloy particle extends outward from the particle's actual location on the surface of the coating. Cell membrane 125 that covers the cyprid body also covers the walking appendages 119, but is not shown as a separate layer on the walking appendages 119. The thoracic swimming muscle structures 118 and caudal walking antennae (“walking legs” on head) 119 muscle structures of the larval form is thrown into spasm because of inhibition (blocking) of gamma aminobutyric acid (GAB A) receptors represented by structures 126 on cell membrane area 123 on these walking appendages caused by the copper in these alloy particles. Furthermore, such inhibition of the GABA receptors on the cell membranes of the larval forms sensitizes another receptor, the TRPV1 receptor, so that the larval forms become more sensitive to the presence of capsaicinoid compounds that may be impregnated into outer layer 98 along with the CuZnSn alloy and other chemically active substances as will be explained later in producing noxious “pain” signals. The muscular spasms caused the cyprid to be repelled off the surface of the coating to settle somewhere else.

In the case of veliger larvae of invasive mussels, it is the veliger “foot” (not shown) that performs this surface exploring and attachment function. It has been shown that the surface of the outer polymer layer exposed to the surrounding water needs to have only 30% of its area impregnated with exposed alloy particle powders to have total larval repulsion ability across the entire outer polymer layer surface because of the extent of the alloy particle's chemical influence beyond the actual location of the particle itself within the polymer matrix of outer layer 98. The tin prevents the dezincification exit of zinc atoms out of the alloy, as described above, which would otherwise weaken the alloy and allow release of copper atoms into the water. Additionally, the local presence of zinc atoms in the alloy may be in equilibrium with chelated zinc atoms contained within another chemical substance in the outer polymer layer, such as zinc pyrithione 108, thereby preventing the zinc pyrithione from dissociating into Zn+2 ions and pyrithione-1 ions with subsequent leaching into the surrounding water. Thus the presence of the alloy powder in effect makes the zinc pyrithione (ZPT) even more water insoluble than it already is. Copper pyrithione, also used in some ablative paints with and without copper, can be impregnated into the outer polymer layer as an alternative, and the copper in the tin brass alloy powder will prevent that compound from dissociating into copper ions and pyrithione ions which will then leach undesirably into the water.

The presence of the alloy will retard chemical and galvanic corrosion against the coating and the underlying structural surface being protected, especially by seawater. Furthermore, not only does blocking the GABA receptors of the larval forms by the copper in the tin brass alloy powder prevent proper settlement and body movement, but the copper also interferes with the developing larvae so that those larvae that were not repelled off the surface cannot develop further by inhibition of chemical processes in their cellular membranes. Thus cyprid and veliger development and progression to the next stage of development, the juvenile mussel or barnacle 114, is prevented thereby preventing the penetration of the outer polymer layer 98 and the subsequent attack on the inner polymer layer 99 as shown in FIG. 2 .

In addition, touching of the copper atoms in the alloy powder by the antennae “walking legs” of the larvae causes disruptions in the integrity of their cell membranes causing them to drop away from the surface of the coating. This occurs because wherever the larvae touch the surface of the outer polymer layer with their cellular membranes, the copper atoms in the alloy is converted to copper ions in the vicinity of that cellular membrane making for an unfavorable environment for attachment, settlement, and progression to the juvenile stage. It is a very similar phenomenon to the manner in which a brass door knob inhibits bacterial growth on its surface.

The inclusion of tin in the alloy is totally safe for the environment with no known toxicity of significance. The use of tin in this application to repel animal biofouling organisms has no relationship to the organotin compounds (TBT). Whereas organic tin compounds can be toxic to the aquatic environment, the inorganic tin described herein is not. Like the copper and zinc of this alloy, the tin also does not leach into the surrounding water because of the interatomic forces holding together metal alloy atoms together. The alloy 107 is insoluble in water and totally non-reactive with either saltwater or freshwater. Furthermore, not only is the alloy 107 non-ablative, but also the polymer 116 in the outer polymer layer 98 is non-ablative. Though all of the tin remains in the alloy, the doping of the alloy with small amounts of tin enhances the antifouling effect over that of plain non-tin brass alloys. Thus, because all component atoms of this alloy remains in the alloy, and the manner in which the alloy is used in this outer polymer layer of the polymer coating where it remains entrapped in the polymer matrix, this cupro-metallic alloy is safe for the environment and remains unchanged physically and chemically from exposure to the surrounding water for extremely long periods of time.

A further component of the outer polymer layer 98 is a chemical component 109, which may include a capsaicin or capsaicin-like material, such as nonivamide. Nonivamide is a synthetic capsaicin-like material, similar to capsaicin and capsaicinoids that occur naturally in chilis and other plants. Nonivamide has a Scoville heat unit (SHU) pungency rating of 9.5 million when in 100% purity. Nonivamide is over half as potent as the strongest natural cap saicinoid. Nonivamide is non-volatile and water insoluble. Nonivamide may be substituted by any of the capsaicinoid compounds known to naturally occur in species of chili pepper, crushed extract powder or oil of the chili pepper itself, or it may be substituted by any synthetic compound with capsaicinoid properties that act as an agonist to the capsaicinoid receptor (TRPV1) receptor.

When the outer polymer layer 98 is impregnated with a chemical 109, such as nonivamide, it protects the coating from bio-proliferative processes that would destroy the coating and the protected submerged surface structure beneath it. The capsaicin-like chemical 109 stimulates a receptor on the biofouling animal organism, the TRPV1 receptor, also known as the capsaicin or vanilloid-1 receptor, structure 121 on FIG. 2 , located in “walking leg” cell membrane area 120. The stimulation of this receptor causes a noxious stimulus, analogous to pain in higher evolutionary organisms such as mammals, to be felt by the settling larval forms of barnacles (cyprids) and invasive tiger and quagga mussels (veligers), as well as other biofouling animal organisms, including both calcium and non-calcium forming animal organisms. The reaction to the chemical 109 causes an instant recoiling of the organism off the surface, thus repelling them from the coating to settle elsewhere.

The TRPV1 receptors 121 can be made more sensitive to capsaicinoid compounds when GABA receptors on the cell membrane (area 126 on FIG. 2 ) close by are inhibited by copper atoms or ions provided by the interaction of the larval cell membrane with the copper in the tin brass alloy powder. The TRPV1 receptors are located in the “walking legs” 119 of the cyprids. The TRPV1 is represented by structure 121, located in “walking leg” cell membrane area 120. Tunicates, such as the problematically invasive tunicate, Morula Manhattensis (also known as Sea Grapes or Sea Squirts), also possess these receptors. In that, the activation of this TRPV1 receptor by nonivamide is similar in action to that of the blockage of the GABA receptor by entrapped copper atoms in the alloy 107, with both operating together in a synergistic manner to cause repulsion of the larval forms off the surface of the coating and its outer polymer layer, preserving the integrity of that layer. The capsaicin-like chemical 109 may have a purity of 95% or greater, and its compositional weight in the outer polymer layer may be about 1% to about 10%, with a specific illustrative value of 3%.

The bilayer coating may further include a chemical substance known as medetomidine 110, as shown in FIG. 1 . Medetomidine 110 may be impregnated into the outer polymer layer 98, to synergistically enhance the repulsion effect of the nonivamide 109 and alloy powder 107 on bio-proliferative processes caused by settlement of larval forms of biofouling animal organisms, as a further mechanism to protect the outer polymer layer of the coating, which, in turn, protects the inner polymer layer 99 of the coating. Like the nonivamide 109 and the powder alloy 107, the control mechanism of the medetomidine 110 for bio-proliferative processes attacking the coating will be its interaction with a cell membrane receptor on the invading larval biofouling animal organism, known as the octopamine receptor represented by structure 122 on cell membrane area 127 of the “walking legs” 119, analogous to the alpha-2 adrenergic receptor in mammals and humans responsible for blood pressure control and other functions. The d-isomer of medetomidine, dexmedetomidine, can be used as well.

Clonidine, used as a human anti-hypertensive medication will also stimulate the octopamine receptor. For the purposes of this invention, medetomidine, dexmedetomidine, or clonidine or any other compound that can stimulate the alpha-2 adrenergic receptor in mammals and humans, can be used as chemical 110 in a non-ablative coating comprised of a polymer 116 impregnated with these chemical substances. These chemical substances are effective in concentrations by weight of about 0.01% to about 10%. Sensitivity of the octopamine receptor to these agents allows for extremely small concentrations to be effective, with an illustrative range of about 0.01% to about 1% by weight composition of the outer polymer layer 98 being specifically contemplated.

The octopamine receptor was named for the human pharmacological agent, Octopamine, also known as Synephrine, a human decongestant. In addition to octopamine, medetomidine, dexmedetomidine, and clonidine, the following biologically and chemically active agents that are alpha2-adrenergic receptor agonists (stimulants) may be used as chemical 110: Fadolmidine, Guanfacine, Guanabenz, Guanoxabenz, Guanethidine, Xylazine, Tizanidine, Methyldopa, Methylnorepinephrine, Norepinephrine, Amitraz, Detomidine, and Lofexidine. Other chemical substances that may be included as the chemical 110 would be chemical substances that effect both alpha-1 and alpha-2 adrenergic receptors, such as Xylometazoline, Oxymetazoline, Apraclonidine, Cirazoline, Epinephrine, Ergotamine, Etilefrine, Indanidine, Mephentermine, Metaraminol, Methoxamine, Mivazerol, Naphazoline, Norfenefrine, Phenylpropanolamine, Propylhexedrine, Rilmenidine, Romifidine, Synephrine, and Talipexole. Any of these drugs may be used in this described manner to repel biofouling animal organisms from the outer polymer layer 98.

Like the alloy powder 107 affecting the GABA receptors to induce muscle spasm in the biofouling larval forms, resulting in repulsive behavior of the larvae from the submerged surface, and the nonivamide affecting the TRPV1 receptor, causing withdrawal of the walking appendages of the larvae from the submerged surface causing a repulsive behavior, the medetomidine, dexmedetomidine, methyldopa, oxymetazoline, or clonidine and other drugs of this class, by stimulating the octopamine larval receptors, causes the cyprid walking legs to go into severe spasm and convulsive shaking, preventing settlement. The organism then cannot settle on the coating service, and thus has to try to settle somewhere else. In accomplishing the stimulation of the octopamine receptors, it synergistically reacts with the alloy powder 107, blocking the GABA receptor, and the nonivamide 109, stimulating the TRPV1 receptor, and the action of all of these effects on the larvae membrane receptors forces the larvae to disengage from the protective outer polymer layer 98 and float away back into the water to try to settle someplace. This process of repulsion from the surface of the outer polymer layer is illustrated in FIG. 2 . The synergistic combination of simultaneous activity of these three types of chemical compounds in the same outer polymer coating layer on three different receptor sites of the larval membrane provides for an efficient and effective method of repulsing the biofouling larvae before they permanently attach themselves to the coating and begin to develop into juvenile biofouling animal organisms. The effects on all three biofouling animal membrane receptors are reversible, and that effect dissipates once the animal is repelled from the surface, so that the organism is not permanently harmed. Such an arrangement of multiple receptor modulating chemical agents being placed within the same polymer layer has not been previously described. The resulting high effectiveness through synergistic pharmacologic pathways involving three different pharmacologic sites of activity and three different biological receptor sites have not been employed before in a coating system designed to protect a coating and its coated surface and structure from damage, deterioration, and discoloration from bio-proliferative processes.

A further component that may be used in the outer polymer layer 98 is zinc pyrithione (ZPT) 108. The outer polymer layer 98 may be impregnated with water-insoluble and water-non-reactive zinc pyrithione to prevent proliferative biological processes that include fungal, bacterial, and algal organisms. Combined with the other chemical substances impregnated in the outer polymer layer, ZPT will inhibit calcium formation from, e.g., barnacles, ship worms or marine borers, and invasive mussels, and will further prevent and non-calcium—forming organisms, including tunicates such as Golden Hearts and Sea Grapes, from producing an infiltration into the outer polymer layer. This prevents the discoloration, corrosion, damage, deterioration, and disruption of that outer polymer layer 98. It also has activity in preventing proliferation of the Sea Grape tunicate, Morula manhattensis, when it is combined with cupro-metallic elements such as cupro-nickel, brass and bronze powders and nonivamide. The combination of cupro-metallic alloy powder, Zn+2 ions, Pyrithione-1 ions, TRMV1 receptor effects of nonivamide, all interfere with the settlement of ova and sperm from these tunicates onto the outer polymer layer 98, and also causes withdrawal from the surface. This combination of chemically active substances is the only known combination that has effectively inhibited the rapidly proliferating invasive species known as the tunicate, Morula manhattensis.

Furthermore, ZPT inhibits ATP synthesis and cellular breathing in biofouling animal organisms, causes severe iron starvation, and produces DNA damage. When the cupro-metallic alloy powder 107 is added, the repulsive effects of the coating are enhanced over just using the zinc pyrithione (ZPT) 108 and the nonivamide 109 with or without the medetomidine. This novel combination of alloy powder 107 with ZPT 108 is effective against all known biofouling plant and animal organisms, even when tested without the nonivamide 109. The combination of all three of the ZPT 108, nonivamide 109, and the alloy powder 107 is synergistically the most effective composition against these tunicates and this result can be further enhanced through the incorporation of medetomidine or a similar chemically active agent in the same class of chemical compounds that was enumerated above.

The manner in which the ZPT is used in the coating is unique in several other respects. ZPT is not emitted into the water, in contrast to the action of a decomposing ablative copper paint, but rather is held fixed in a water-insoluble state within the highly stable matrix of the polymer 116 of the outer polymer layer 98, with ZPT molecules being exposed but fixed in location only at the surface of the outer polymer layer 98. The presence of the powdered alloy 107 retards any tendency of the ZPT 108 to dissociate into its components and dissolve in the water. The outer polymer layer 98, which has the ZPT 108 impregnated within it, is in a different layer than that of a cupro-metallic substance, which is in the inner polymer layer 99, thereby preventing the ZPT 108 from chemically reacting with the cupro-metallic substance (such as a copper salt). Such a reaction would otherwise produce copper pyrithione, which is more harmful to the environment than ZPT.

This is a serious problems with ablative paints that have both ZPT and a cuprous salt in one paint layer. The ablative paint layer sheds the combination of the two chemical agents into the water, allowing the formation of copper pyrithione in the water environment along with the dissolution of the hydrolysable acrylic co-polymer paint matrix (e.g., self-polishing or soft ablative paint) or the chemicals are released into the water with the paint matrix remaining intact (e.g., hard ablative paint). This conversion of ZPT to copper pyrithione never occurs in the present embodiments. Not only is the ZPT entrapped within the outer polymer layer, the cuprous salt, copper, or metallic copper alloy is trapped within the inner polymer layer, so that the two never touch. In addition, because neither layer is ablative, neither chemical agent makes it into the water to allow for the production of copper pyrithione (CPT) and daughter products, copper and pyrithione ions.

Note that CPT, like ZPT, is very poorly soluble in water. Normally only a small amount of daughter products (copper and pyrithione ions) that are toxic to the environment are produced. However, in an ablative paint, CPT, like ZPT, is widely disbursed into a body of water such as an ocean, harbor, or lake over a considerable amount of time, until the entire chemical agent load (with or without the paint coating on the boat) has been discharged into the water. In such circumstances, a very large amount of chemically active substance is released and has been shown to produce highly undesirable effects on the aquatic environment for both products.

In the case of the ZPT, the zinc ions are generally non-toxic to the aquatic environment, while the pyrithione ion is, and with CPT, both the copper ions and the pyrithione ions are toxic to the environment. In fact, with an ablative paint coating, the entire ship's coating load of ZPT, and (in a few cases of paint coatings, CPT as well), as well as the entire ship's load of whatever copper salt is used in the ablative paint, would be discharged into the body of water over a one to two year period of time.

None of this occurs with the embodiments of the present invention. CPT can be used in the outer polymer layer of the present coating in the same manner, and with the same effectiveness, as ZPT, because the coating is non-ablative and CPT, like ZPT, would be entrapped in the matrix of the polymer of the outer polymer layer. However, because CPT is trapped in the polymer matrix of outer polymer layer 98, and the copper atoms in the tin brass alloy powder would stabilize the cupper atoms from going into solution as cuprous and cupric ions, like ZPT which is stabilized by the same two exact mechanisms, it may be used with safety to the environment. Because copper ions are more problematical to the environment than are zinc ions, even though the amount of zinc or copper ions that would be released into the water is miniscule, CPT may be used in the inner polymer layer as would other copper salts, because the chemically active agents in the inner layer never touch the water. However, CPT is also safely useable within the coating layer structure of this invention.

In addition to the physical separation of these compounds, the outer polymer layer 98 covers and shields the inner polymer layer 99 to prevent the interposition of seawater, which would otherwise trigger the conversion of ZPT to copper pyrithione if the twos substances were to come into contact with one another.

ZPT also mitigates and eliminates the bio-proliferative processes of scum, algae, fungal, and bacterial proliferation. If these processes are left uncontrolled, aside from providing increased nourishment to larval forms of biofouling animal organisms trying to settle, a thick biofilm layer may form, such that larval forms may never reach down to touch the surface of the outer polymer layer 98 with its repulsive biological active substances. By preventing the formation of such a biofilm, the inclusion of ZPT prevents the larvae from settling and developing into juvenile forms which would be able to penetrate the outer polymer layer 98.

The outer polymer layer 98 thus forms a system comprised which may include different components, some of which may be water-insoluble chemical ingredients, and which may include cupro-metallic alloy powder 107, nonivamide 109, medetomidine 110, and zinc pyrithione (ZPT) 108 impregnated into a polymer coating 116 to form a structural coating layer that will prevent both calcium- and non-calcium—forming organisms from positioning themselves onto and within the outer polymer layer 98 of the coating, thereby preventing its discoloration, corrosion, damage, deterioration, and disruption from proliferative biological process caused by such biofouling animal organisms as well as plant organisms. These components of the outer polymer layer 98 give long-term, multi-year protection of the inner polymer layer 99, and hence the protected surface structure underneath that inner polymer layer, not only from the bio-proliferative processes, but also the chemical, galvanic, and corrosive processes that emanate from within the surrounding water that are exacerbated by the bio-proliferating processes if the latter are uncontrolled.

The synergistic activating effect of the nonivamide 109, medetomidine 110, and the alloy powder 107 on three separate biological membrane receptors of the larval forms, cyprids of barnacles, and veligers of invasive quagga and zebra mussels, and other types of biofouling animal organisms, enhances the efficacy of the outer polymer layer 98. Simultaneous activation of 3 classes of larval membrane receptors simultaneously, including octopamine receptors by medetomidine (and similar chemicals), TRPV1 receptors by nonivamide, and GABA receptors by the alloy powder, which all produce repulsive convulsive activity in the muscle or contractile organs of the larvae of these biofouling animal organisms, ensures that the great majority of the larval forms will be repelled. Thus, even if an individual larval form may have developed resistance in the form of a receptor type and is resistant to the complimentary chemical substance stimulating or blocking it because of mutational variants developing during proliferation, it is highly improbable that a larval form will be resistant simultaneously to all three of these chemical substances used in the outer polymer layer 98.

The number of larval forms that actually do settle on the outer polymer layer 98 is reduced to a miniscule amount, which means the number of larval forms that settle and develop into juvenile forms that can puncture through the outer polymer layer 98 and into the inner polymer layer 99 will also be miniscule. Thus the integrity of the inner polymer coating 99 and secondarily the submerged protected surface structure 105 is extended for a much longer period of time. This ensures the integrity of the outer polymer layer 98, which in turn is responsible for protecting and maintaining the integrity of the inner polymer layer 99 by preventing corrosion, damage, and deterioration of the inner polymer layer 99 from chemical, ultraviolet, galvanic, and proliferative biological processes initiated in and from the surrounding water. These cell membrane receptor active chemical structures, alloy powder 107, nonivamide 109, and medetomidine 110 (and similar compounds), plus the biological activity of zinc pyrithione, plus the extremely durable, UV and chemically resistant polymer 116 (e.g., PUR or FUR) produces an outer polymer layer 98 that is completely non-ablative and that produces a mechanism of protection for the outer surface of the polymer coating structure, and hence the rest of the polymer coating and the protected surface underneath, and at the same time prevents chemical contamination of the surrounding water.

The inner polymer layer 99 further includes measures to protect it from any agents that make it past the outer polymer layer 98. This further protection of the inner polymer layer 99, which further protects the underlying submerged surface structure, may include additional components of the coating. One such component of the inner polymer layer 99 may be an epoxy polymer 115, of which there are many varieties including single component systems, two component systems, moisture cured epoxies, and epoxies capable of curing underwater, as well as epoxy systems that can also function as metal rich (aluminum or zinc) epoxy primers. The epoxy polymer 115 may be applied to structures prior to their submergence into seawater or freshwater which is the usual case. However, there are certain advantages of employing an epoxy that can cure underwater. The nature of this epoxy polymer, which is the preferred embodiment of this invention, allows hardening and curing underwater, so that the epoxy polymer 115 can be applied to structures that cannot be removed from standing water, or it can be applied to structures that have already been placed in the water or to structures that are intermittently in water but cannot be removed from water such as bridge pylons in a tidal body of water. The epoxy polymer 115 may not be resistant to ultraviolet light, but that protection is afforded by polymer 116 of the outer polymer layer 98; PUR is UV resistant, and FUR is exceptionally UV resistant. The epoxy polymer 115 may have a high adhesion to the underlying protected surface 105, for example being able to resist a pulling pressure of up to 2500 pounds per square inch as in the case of the epoxy polymer system. The epoxy polymer 115 may be somewhat flexible, and thus may be resistant to flexing movements of the submerged surface as in the case of the epoxy polymer system. While a specially formulated epoxy material may be used to achieve these purposes, any suitable epoxy polymer having these characteristics listed above may be used, including zinc- and aluminum-rich primers. An inner primer polymer layer 104 may be used.

Chemical substances may be added to the inner polymer layer 99 to protect the coating and against damage caused by bio-proliferating processes of a biofouling nature. Not all biofouling larvae are stopped at the outer polymer layer 98. A certain small percentage of the larval forms that are supposed to be repelled by the outer polymer layer may not be repelled, for example because they are resistant or because they develop resistance by the chemoreceptors of their “walking legs” even to the wide array of synergistic chemical compounds in that layer designed to repel them off the surface of the outer polymer layer 98. These larval forms 117B, referring to FIG. 2 , may settle and proceed to grow into juvenile barnacles 114, mussels, marine shipworms, tubeworms and so forth, leading to minute punctures of first the outer polymer layer 98 and then the inner polymer layer 99. This would be normally the first step in the compromise of the polymer coating, as these juvenile animals would mature into mature adult biofouling animal organisms.

However, when the larva, now a juvenile form 114, punctures the interface boundary 128 between the two polymer layers, and its cellular membrane, designated by cell membrane area 124, that is now attached to cupro-metallic compound particle 129, the juvenile form 114 will encounter chemically and biologically active cupro-metallic and other substances that will interfere with the biofouling animal's metabolic processes to the point of immediately stopping its growth and development, and shortly afterwards causing its demise, thus preventing further damage and loss of integrity of the inner polymer layer 99 and to the entire coating as a whole. The inactivated or deceased juvenile barnacle 114A drops away from the polymer coating.

While there are a myriad of different chemical substances in the inner polymer layer that can be used for this purpose without environmental harm, because the inner polymer layer 99 is covered by the outer polymer layer 98, chemical substances may be used that have some form of copper-containing substance without any negative environmental effect. These chemically active substances can include one or more of a group of copper materials, including cupro-metallic alloys such as cupronickel, cuprozinc (brass), cuprotin (bronze), cuprosilver, and the tin-containing copper-nickel-tin alloy described above. These alloys may be in powdered form, flakes, or cupro-metallic salts that may be either water insoluble or water soluble, but that are capable of reacting either with the chloride ion of seawater or the hydrogen ion of fresh water. The inner polymer layer protects its own integrity using these compounds, and thus protects the integrity of the submerged protected surface structure underneath it, by eradicating and killing on the spot the invading juvenile biofouling organism 114 within the protective coating structure. This is in contrast to the outer polymer layer 98, which repels organisms. Thus, no further structural damage is done to the inner polymer layer 99 or the polymer coating as a whole, or to the protected surface 105 underneath the coating, as further continued growth of the biofouling animal organism into a full adult biofouling animal, the entity which is responsible for damage, deterioration, and discoloration of the coating, is prevented.

In ascending order of effectiveness, the inner polymer layer 99 can be impregnated with any one or more of a group of cupro-metallic substances including copper powder, copper flake, cupro-nickel powder or cupro-nickel nano-powder, cupro-tin (bronze) powder, cupro-zinc (brass powder), cupro-silver alloy, and the copper-zinc-tin alloy that may be used in the outer polymer layer 98 of this invention as well. If the copper-zinc-tin alloy is used in the inner polymer layer 99 as well as the outer polymer layer 98, it may be used in a much higher concentration by weight of the inner polymer layer 99, for example up to as much as 75% by weight of the inner polymer layer 99. At this significantly higher concentration, the metallic copper, either in its native form, or as a cupro-metallic alloy will be lethal to the invading juvenile organism 114, inducing within it copper heavy metal enzyme dysfunction by the following mechanisms: cellular membrane disturbance and damage, free radical oxygen species generation, and damage to proteins, enzymes, RNA, and DNA. Copper atoms or ions in high enough concentrations are lethal to the juvenile organisms, rather than just causing repulsion and settlement prevention via blockage of the GABA receptors in the larval forms at the lower concentration of the cupro-metallic alloy powder 107 used in the outer polymer layer 98.

Mixtures of cupro-metallic salts, both water insoluble salts and water soluble salts, are even more effective in arresting bio-proliferative processes at the interface 128 of the inner polymer layer 99 and the outer polymer layer 98 than just employing metallic copper or cupro-metallic alloys. To maximize the eradicating power of the inner polymer layer 99, certain embodiments in this invention employ a mixture of copper-zinc-tin alloy with a cupro-metallic salt. The cupro-metallic salt mixture may cuprous oxide, because it is water insoluble and for its efficacy in producing cuprous Cu+1 ions and copper hydroxychloride (Cu₂(OH)₃Cl), also known as tribasic copper chloride, that are deleterious to bio-proliferative biofouling animal organisms. While being more water soluble than cuprous oxide, whereas cuprous oxide reacts with salt water to give copper hydroxychloride, the copper hydroxychloride does not react any further with seawater. The combination of high concentrations of cupric ions (that change to cuprous ions) from the copper hydroxychloride, with the direct copper effects from the powder alloy, is especially efficacious. The combination of impregnating both cuprous oxide and copper hydroxychloride into the inner polymer layer is also especially efficacious as a source of cupric and cuprous ions to eliminate the proliferation of the juvenile biofouling animal organisms before they destroy the coating.

In general, the Cu+1 cuprous salts such as cuprous thiocyanate, cuprous oxide, cuprous sulfide tend to be water insoluble (with some exceptions such as cuprous sulfate which is water soluble), and the Cu+2 cupric salts tend to be water soluble, with some of them coming in the form of either hydrated crystalline form or anhydrous form. The cupric salts tend to range from mildly soluble in water such as cupric hydroxide or cupric (copper) hydroxychloride to very soluble in water, such as cupric sulfate, cupric nitrate, cupric chloride, and cupric gluconate. There are exceptions to these rules as cupric oxide, cupric thiocyanate, and cupric (copper) pyrithione (CPT) are also insoluble in water. The cuprous Cu+1 are more efficacious in this purpose of protecting the coating than are the cupric Cu+2 ions, and when Cu+2 ions react with the Cl-1 and other anions of seawater or the H+ ions in freshwater, the desirable Cu+1 ions are produced. However, any of the other water insoluble cupro-metallic salts can be used, including any one from a group comprising of cuprous oxide, cuprous chloride, cuprous iodide, copper napthenate, copper resinate (reaction product of copper carbonate hydroxide with rosin), cuprous thiocyanate, cuprous sulfide, cuprous bromide, cuprous fluoride, cuprous hydroxide and cupric oxide which are all water insoluble like the cuprous oxide salt, as representative examples of this class of cupro-metallic salts. Cupric thiocyanate is water insoluble like the cuprous thiocyanate. Also, cupric pyrithione is water insoluble and cupric (copper) hydroxychloride is only slightly soluble in seawater. Furthermore, because of the bilayer structure of this coating, in which the outer polymer layer 98 covers the inner polymer layer 99, even if the cupro-metallic salt used were water soluble, the salt would stay within the coating and does not leach out into the surrounding water. Cuprous thiosulfate has two distinct advantages in that it can be used on an aluminum or steel hull without a primer, because it will not react in a galvanic manner to the hull metal, and it has a strikingly white color which avoids the need for additional white pigment when other salts such as cuprous oxide are used that generates a pinkish color to the boat's hull, which is considered undesirable by some boat owners who demand a white color to their hulls. To cover the pink color of cuprous oxide and other salts, a pigment may also be added to outer polymer layer 99.

Water soluble cupro-metallic salts that could be used in this invention, in either their hydrate crystalline state or anhydrous form, include one of a group comprised of the following: cuprous chloride, cupric chloride, cupric sulfate, cupric nitrate, cupric acetate, and are representative salts of this class of cupro-metallic salts. Mixtures of more than one cupro-metallic salt from the same group of cupro-metallic salts or from both groups of cupro-metallic salts may be used. Mixtures of water soluble and water insoluble cupro-metallic salts may be used, with or without cupro-metallic pure metal and/or cupro-metallic alloys, to give a wide range of functional compositions using forms of copper in inner polymer layer 99, which can be chosen on the basis of the particular application required and economic factors required for the desired application. A preferred mixture is a mixture of cuprous oxide, which when exposed to seawater and the chloride ion due to a juvenile biofouling organism piercing the outer polymer layer exposing a microscopically small area of the inner polymer layer to sea water, changes to copper hydroxychloride and copper hydroxychloride itself which does not react any further with seawater giving the coating a self-sealing property. This self-sealing property will also protect the inner polymer layer and the protected surface underneath in the event of an abrasive injury to the outer polymer coating from passing debris in the water as well; the very nature of and the intrinsic flexibility of the PUR and the FUR used in the outer polymer layer contributes to the self-sealing ability of the coating.

Note that in freshwater, where there are few chloride ions to drive the chemical reactions that most cupro-metallic salts use to produce cuprous ions in as large a quantity as with seawater, one can use cuprous oxide because of the reaction of this salt with the elevated H+ ion level often found in freshwater bodies of water. All of the above copper-related chemistry, because of the unique bilayer structure of the coating and its non-ablative nature, occurs within the coating itself and not in the surrounding aquatic environment. The location of the active chemistry at the level of the inner polymer layer 99 accounts for eradication of organisms that managed to pierce the outer polymer layer 98. In the same manner that nonivamide 109, medetomidine 110, and powdered cupro-metallic alloy 107 impregnated into the outer polymer layer prevent damage, deterioration and discoloration to that outer polymer layer 98 of the protective polymer coating as well as the inner polymer 99 layer below it, the cupro-metallic substances impregnated within the inner polymer membrane protect that layer, the coating itself, and the submerged protected surface structure below it from damage from seawater and freshwater processes, especially the bio-proliferative processes which would otherwise open the way for additional damage to the polymer coating from chemical, galvanic, and corrosive processes originating in and from within the surrounding water.

Various combinations of the above-described features can be used to form a polymer coating. In one such combination, the outer polymer layer 98 may be include a polyurethane or fluorourethane polymer that is impregnated with zinc pyrithione or another metal pyrithione, in particular, copper pyrithione; medetomidine, dexmedetomidine, clonidine, or similar substance affecting the octopamine receptor; nonivamide or another capsaicinoid substance; and a copper-zinc-tin alloy powder. The inner polymer layer 99 may include an epoxy layer incorporating any epoxy system with a high adhesiveness to the underlying substrate protected surface and a preferential ability to cure underwater and that is impregnated with a water insoluble cupro-metallic salt (e.g., cuprous oxide), a water soluble cupro-metallic salt (e.g., cupric sulfate), pure elemental copper powder or flake, and/or cupro-metallic alloys (e.g., copper-zinc-tin alloy).

By example, another such combination, the outer polymer layer 98 may include a polyurethane or fluorourethane polymer that is impregnated with zinc pyrithione; nonivamide; and a copper-zinc-tin alloy powder. The inner polymer layer 99 may include an epoxy layer that is impregnated with a water insoluble cupro-metallic salt (e.g., cuprous oxide), a water soluble cupro-metallic salt (e.g., cupric sulfate), pure elemental copper powder or flake, and/or cupro-metallic alloys (e.g., copper-zinc-tin alloy).

In another such combination, the outer polymer layer 98 may be include a polyurethane or fluorourethane polymer that is impregnated with zinc pyrithione; medetomidine, dexmedetomidine, clonidine, or similar substance; and a copper-zinc-tin alloy powder. The inner polymer layer 99 may include an epoxy layer that is impregnated with a water insoluble cupro-metallic salt (e.g., cuprous oxide), a water soluble cupro-metallic salt (e.g., cupric sulfate), pure elemental copper powder or flake, and/or cupro-metallic alloys (e.g., copper-zinc-tin alloy).

In another such combination, the outer polymer layer 98 may be include a polyurethane or fluorourethane polymer that is impregnated with medetomidine, dexmedetomidine, clonidine, or similar substance and a copper-zinc-tin alloy powder. The inner polymer layer 99 may include an epoxy layer that is impregnated with a water insoluble cupro-metallic salt (e.g., cuprous oxide), a water soluble cupro-metallic salt (e.g., cupric sulfate), pure elemental copper powder or flake, and/or cupro-metallic alloys (e.g., copper-zinc-tin alloy).

In another such combination, the outer polymer layer 98 may include any combination of components described herein. The inner polymer layer 99 may include an epoxy layer that is impregnated with cupro-metallic alloy (e.g., copper-zinc-tin alloy) powder in a high concentration by weight with either cuprous oxide or copper hydroxychloride, with a total cupro-metallic substance being up to 75% of the inner polymer layer 99 by weight.

In another such combination, the outer polymer layer 98 may include any combination of components described herein. The inner polymer layer 99 may include cuprous oxide, with or without copper hydroxychloride, with a total cupro-metallic substance being up to 75% of the inner polymer layer 99 by weight.

In another such combination, the outer polymer layer 98 may include any combination of components described herein. The inner polymer layer 99 may include a mixture of any two compounds selected from water-soluble cupro-metallic inorganic salts, water-insoluble cupro-metallic inorganic salts, copper-zinc-tin cupro-metallic alloy, or pure elemental copper metal flake or powder.

These are just a handful of different combinations that are contemplated. In each of the combinations, the polymer coating is non-ablative in both polymer layers, and remains intact during the entire operational life of the coating. Each composition of the polymer coating may include copper and related cupro-metallic substances that used in a non-ablative manner that is safe for the aquatic environment.

Thus, the coatings described herein can promote aquatic environmental safety by the use of the copper-zinc-tin powder alloy in the outer polymer layer 98, which protects the integrity of that layer, the use of a synthetic capsaicinoid (e.g., nonivamide) in the outer polymer layer 98 to protect the integrity of that layer, the separation of ZPT in the outer polymer layer 98 from cupro-metallic compounds in the inner polymer layer 99 to prevent the formation of copper pyrithione on the surface of the coating, the use of a mixture of cuprous oxide and copper hydroxychloride in the inner polymer layer 99 to protect the integrity of that layer from bio-proliferative processes, and the use of water-soluble cupro-metallic salts in the inner polymer layer 99 to protect the integrity of that layer in a manner that is safe for the aquatic environment.

The use of the element copper in two different chemical forms simultaneously, in two non-ablative layers, where the copper is in an elemental alloyed powder form in the outer polymer layer 98, and the copper is in a cupro-metallic salt in the inner polymer layer 99, with or without elemental copper either in a pure elemental powdered or flaked state, or in an alloyed elemental powdered state, protects the integrity of the inner polymer layer and the submerged surface structure beneath it. Mixing water-soluble and water-insoluble cupro-metallic salts together, with or without the presence of the copper-zinc-tin powder alloy or pure elemental copper in the inner polymer layer 99 enhances the production of copper ions within the inner polymer layer 99 to prevent damage to the inner polymer layer 99 by bio-proliferative processes that would otherwise attack that layer, and such protection of the inner polymer layer leads to protection of the coating itself and the protected submerged surface structure underneath it.

The non-ablative outer polymer layer 98 protects the integrity of the inner polymer layer 99 of the coating beneath by preventing chemical, galvanic, corrosive, mechanical abrasive and frictional, radiant (UV), and bio-proliferative processes emanating from the surrounding water from reaching and damaging the inner polymer layer. The non-ablative outer polymer layer 98 protects the integrity of the non-ablative inner polymer layer 99, which, in turn, protects the integrity of the entire non-ablative polymer coating, which in turn protects the integrity of the submerged protected surface structure.

The coating structure of one non-ablative outer polymer layer 98 covering a second non-ablative inner polymer layer 99 allows complete containment of the chemical substances impregnating the inner polymer layer 99 within that layer, thereby allowing the use of a wide variety of cupro-metallic substances to be used with complete safety to the surrounding aquatic environment in the process of protecting the submerged surface structure beneath it. Such a bilayer non-ablative structure allows, in addition to or instead of a cupro-metallic chemical substance, any chemical compound or combinations of chemical compounds that can be used to protect the inner polymer layer 99 from damage, corrosion, deterioration, and discoloration caused by bio-proliferative processes and secondary damage from chemical, galvanic, and corrosive processes resulting from such bio-proliferative processes, as long as the chemical substances impregnating the inner polymer layer are physically and chemically compatible with each other and with the polymer constituting the inner polymer layer 99.

Given that boat hulls and other structures can be painted with up to a dozen layers of coating, the number of inner polymer layers in addition to the outer polymer layer 98 comprising the complete polymer paint coating may exceed one, and as many as a dozen such inner layers, with adjacent layers containing the same assortment of biologically and chemically active substances to result in thicker inner polymer layers, or adjacent layers can contain different biologically and chemically active substances and compositions so as to create a myriad of possible embodiments and extensions to the protective polymer coating compositions comprising the principles and features of this invention.

To explain further the protective mechanisms to the coating that happens at the inner polymer layer 99, copper ablative paint is used in all bodies of water throughout the world, causing excessively high and toxic copper concentrations that are detrimental to the aquatic environment, especially in areas of high shipping density and low water velocity such as harbors and marinas. Certain legal jurisdictions, such as the State of Washington, had banned the use of copper antifouling paints, and the State of California had planned to do so, only to refrain because of a lack of any suitable alternatives that worked against biofouling contamination of ship hulls. However, the inner layer 99 of the multi-layer coating described herein can be impregnated with a cupro-metallic salt that is water soluble or insoluble, with or without elemental copper in either a pure elemental powdered form or an alloyed powder form at a weight concentration of 5% through 75%. That cupro-metallic substance, be it a copper salt, elementally pure copper, or cupro-metallic alloy, never leaches into the water.

In contrast, ablative copper paints may employ multiple layers, but the purpose of the multiple layers is for producing on the ship's hull a paint coating of desired thickness with each layer having the same composition as the layer underneath. The purpose of the top layer of copper ablative paint is the same as the underneath layer of copper paint. All of the layers are ablative and discharge their load of copper substance into the water surrounding the ship with (soft ablative paint) or without (hard ablative paint) disruption and discharge of the paint matrix and its resulting breakup products into the water.

Using non-ablative materials, where chemical substances are sequestered in different polymer layers, produces compositionally different polymer layers whose function is different from each other and where the function of the outer polymer layer 98 is executed to protect the inner polymer layer 99 underneath first, and then the function of the inner polymer layer is executed next in a sequential process. The coating and the submerged protective surface are protected by first repelling larval forms and then by inactivating the juvenile forms that managed to settle in spite of the first layer. As soon as larvae penetrate the boundary between the outer polymer layer 98 and inner polymer 99 layer, being as small as 0.1 mm in diameter, they are be inactivated and eliminated once they touch and penetrate the inner layer.

The presence and absorption of the copper salt or other cupro-metallic substance by the juvenile barnacle or mussel at their point of attachment to the surface and the inner polymer layer leads to copper heavy metal disruption of the biofouling animal's cell membrane, enzyme functioning, and disruption of its proteins, DNA, and RNA. This process results in inactivation of the biofouling animal within the coating itself, or on its surface, but not within the water as in the case of the ablative copper paints. Once the biofouling animal is non-functional or deceased, it drops away, leaving a microscopic hole which quickly seals itself with a highly water insoluble copper salt, copper hydroxychloride, made from the interaction of seawater with that infinitesimally small hole and the infinitesimally small amount of cupro-metallic substance that it contains and that remained after the biofouling organism ingested some of the cupro-metallic substance. The sealing ability of the inner polymer layer is made more effective by the natural proclivity of flexible polyurethane and fluorourethane coatings comprising the outer polymer layer that are self-sealing for microscopic defects.

A small amount of cupro-metallic substance is thus absorbed into the biofouling animal organism, and whatever remains exposed is converted into the very poorly soluble copper hydroxychloride, sealing up that tiny hole quickly and preventing any leaching of copper salt or other cupro-metallic substance even from this tiny hole. The flexible membrane of FUR or PUR in the outer polymer layer 98 also helps seal up the miniscule sized hole. Before that happens, the area of exposure to seawater is so small that the tiny amount of cupro-metallic salt in that tiny hole quickly is either exhausted or covered by the relatively insoluble copper salt, (e.g., copper hydroxychloride), which makes up the green patina seen on copper alloys exposed to seawater.

Copper hydroxychloride is also known as dicopper chloride trihydroxide, Copper trihydroxyl chloride, and tribasic copper chloride—(Cu₂(OH)₃Cl). It is also the major toxic product of copper based antifouling paints that is released into seawater, because of the ongoing chemical reaction of the seawater and its chloride ions with the copper salt co-polymer acrylic matrix cross-linker in the ablative paint. However, this same copper hydroxychloride compound in the present polymer coatings serves as a protective seal in the tiny hole created in the inner polymer layer of this invention (as well as actually being a suitable cupro-metallic salt in the inner polymer layer of this invention). There is no meaningful leaching of the cupro-metallic ions into the aquatic environment.

Furthermore, to eliminate one barnacle larva that attached itself to the ship's coating, with conventional ablative paints, the entire submerged ship's hull must be constantly leaching cupro-metallic ions into the aquatic environment during the lifetime of the boat to eradicate that one barnacle that could attach at any time during the operating lifetime of the boat. On the other hand, a boat coated with the two layer polymer coating described herein leaches only a miniscule, negligible amount of cupro-metallic ions through that one 0.1 mm hole for a few hours, before the coating seals itself up after the juvenile biofouling organism has been inactivated. The rest of the boat hull does not leach any cupro-metallic ions into the water.

As an example, a hole left by an inactivated juvenile barnacle will have a diameter of about 0.1 mm. This hole would leach cuprous oxide at a rate of about 1.0 microgram per cm² per day in seawater from a hole area of approximately 9×10⁻³ sq. mm or 9×10⁻⁵ sq. cm. for approximately 2 hours (8×10⁻² day) before it is sealed up. In this example, the hole will thus leach approximately (9×10⁻⁵ sq. cm.)×(8×10⁻² day)×(1.0 microgram/sq. cm./day)=7.2×10⁻⁶ microgram or approximately 10⁻⁵ microgram of copper for each juvenile barnacle that managed to reach the inner polymer layer interface, a virtually unmeasurable amount. Compared to the leach rate of 1.0 microgram per cm² continuously per day, day after day from a ship hull that might have a surface area of 100 m², resulting in a loss of 10⁶ microgram per day for the whole ship's hull, or more than 10¹¹ (100 billion) times as much as what would leach from a larva's breach of the outer polymer layer 98 described herein. And the loss of approximately 10⁻⁵ microgram per day would occur on only that one day when the juvenile barnacle attached itself until the hole sealed up. Even if a hundred juveniles made it to the inner polymer layer interface each day, which would not in all practicality happen, the amount of copper leached into the water per day from those juvenile barnacles as they are eliminated would amount only to 10⁻³ micrograms per day, or still 10⁹ (one billion times) less than with the ablative paint.

Using a more realistic calculation of one juvenile barnacle puncturing the inner polymer layer per day on a reasonably sized ship, with a painted hull area of 100 sq. m., given that the hole will seal itself up in 2 hours, producing a daily loss of approximately 10⁻⁵ microgram as above per juvenile barnacle that made it to the inner layer, and given that a copper ablative paint may release up to 25 micrograms per cm² per day (6-25 times the minimal effective rate of 4×10⁻⁶ micrograms per cm² per day known to be effective for eradicating barnacles), an ablative copper paint will release 2.5×10⁷ micrograms per day from the entire ship's hull (10² sq. m.×10⁴ cm²/sq. m.×25 micrograms/cm²/day=2.5×10⁷ micrograms per day=25 g=approximately one ounce of copper per day) or approximately 10¹² times (one trillion times) as much copper per day by this ablative copper coating covering this reasonably sized ship hull as compared to the 10⁻⁵ microgram copper release per day by the non-ablative coating comprising this invention.

Furthermore, the inner polymer layer 99 with the cupro-metallic salt, elemental copper, or copper alloy, never touches the surrounding aquatic environment because of the shielding of the outer polymer layer 98 that covers and protects the inner polymer layer 99. Hence, there is no leaching of copper in its elemental or cupro-metallic ionic form into the aquatic environment. As a result, the use of copper salts in an antifouling coating can be safely used, and its effect of being an aquatic environmentally contaminant is for the most part eliminated as the two layer polymer coating performs its primary function to protect the submerged surface structure.

Additionally, the use of copper ablative paint-based elimination of biofouling in freshwater is less efficient than site-specific deterrence in marine salt water, and is ineffective in some cases. That is because freshwater contains no chloride ion to interact with the cupro-metallic salt to produce copper hydroxy-chloride. Instead, the copper salt in fresh water reacts with whatever hydrogen ions might be present in the body of freshwater to produce copper ions. This process is variable, because the pH of freshwater can be acidic or basic to varying degrees. Thus, the eradicating effect on freshwater invasive mussels such as the quagga or zebra mussel can be variable and, in some cases, negligible even though the copper and other additives in ablative paints such as ZPT are still released into the freshwater environment in copious amounts. Thus, ablative copper paint is not reliably an effective protection for freshwater immersion of surface structures.

In contrast, in the case of an outer polymer layer 98 as described herein, when the veliger larvae of the invasive tiger or quagga mussel (the most common biofouling animal organisms in freshwater) try to attach to the surface of the coating, they are repelled by the multiple mechanisms described already in detail that are produced by the active chemical agents in that outer polymer layer, and these multiple mechanisms do not need the chloride ion to operate successfully, and thus the outer polymer layer repels the larval forms of the invasive mussels equally as well in freshwater as in saltwater. Furthermore, in the case of an inner polymer layer 99 as described herein, when that inner layer 99 is reached by the occasional juvenile invasive quagga or zebra mussel that made it through the outer polymer layer 98, the point of attachment, known as the pedicle or foot, directly absorbs the cupro-metallic salt or elemental copper into the mussel's body in a significant dose relative to the small size and weight of the miniscule juvenile mussel's body, where it is converted into cupro-metallic ions, resulting in this cupro-metallic salt acting as an efficient internally acting lethal metabolic disrupter. Thus, in the freshwater environment as well, the juvenile mussel is eliminated in a non-ablative way, just as a juvenile barnacle would be eliminated in seawater, all without the leaching of the cupro-metallic ions into the freshwater environment.

While there is no copper hydroxychloride generated in the hole left behind in freshwater scenarios, the leaching of the cupro-metallic substance in the inner layer is only infinitesimal in amount over a few hours because in that tiny hole, the amount of copper that is exposed to the freshwater is miniscule and quickly exhausted. Again, because of its tiny size, the hole still seals up quickly even without the presence of copper hydroxy-chloride because of the other mechanism used by the coating to seal up the hole, namely by the flexible membrane represented by the fluorourethane or polyurethane polymer layer of the outer polymer layer 98. There is no damage to the coating by this hole.

One benefit of the segregation of different chemically and biologically active substances that first repel from the outer polymer layer 98 and then eradicate any biofouling animal organisms from the inner polymer layer 99, by locating the appropriate chemical substances in the outer polymer layer 98 and inner polymer layer 99 respectively, is that unwanted chemical reactions between these different substances are prevented. In contrast, ablative cupro-metallic paints may employ a cupro-metallic salt, mixed together in the same paint layer as zinc pyrithione (ZPT), another chemical substance that has an anti-proliferative effect on some biofouling animal organisms. In such paints, as soon as the paint matrix in the soft ablative paint decomposes into the water, shedding the cupro-metallic salt and the zinc pyrithione into the water together, there is a chemical reaction between the two agents that results in all of the zinc pyrithione being converted into copper pyrithione, because zinc is more chemically active than copper and thus copper replaces the zinc in the ZPT molecule as the zinc goes into solution as its ionic Zn+² form. As a result, copper ablative paints that produce copper pyrithione are very environmentally problematic, as copper pyrithione is extremely long lived, and toxic to aquatic life, much more so then zinc pyrithione. To a lesser extent this undesirable process happens with the hard ablative copper paint, where the paint matrix remains intact, but only the zinc pyrithione and the cupro-metallic salt is leached into the water. However, for the hard ablative paint to work, and for its contained chemical agents to be leached into the water as intended with this paint coating, water has to diffuse into the porous paint layer where this undesirable ZPT copper chemical interaction will occur within the paint coating itself because the ZPR and the copper salt are in the same layer.

In contrast, in a multi-layer coating as described herein, the zinc pyrithione may be in the outer polymer layer 98, and the cupro-metallic salt may be in the inner polymer layer 99, with both layers being non-ablative, so that this undesirable chemical reaction would never occur as the two chemical substances will never be in close proximity to each other. Note that the ZPT does not react with the copper of the Cu Zn Sn tin brass powder, even though they are both in the outer polymer layer 98. Three factors contribute to this: 1) both the ZPT and the brass powder are locked within the matrix of the polymer, 2) the zinc and tin atoms in the alloy powder locks the position of the copper atoms in the alloy solid solution of Cu, Zn, and Sn atoms, and, 3) the two molecules are not surrounded by water, which would otherwise allow the copper to replace the zinc in the ZPT. This contrasts to the case where an ablative paint would allow the zinc and copper atoms to be in close proximity with each other, surrounded by water, which allows the conversion of those atoms to zinc and copper ions, thereby allowing the reaction to form copper pyrithione via ionic replacement chemical and galvanic reactions.

A two layer coating may be placed on the surface to be protected before that surface is submerged in water. However, if a structure cannot be taken out of the water, like that of a pier, dock, bulwark, bulkhead, or bridge pylon, certain polymers can be applied in the presence of water and can be used in the antifouling coating, such as moisture cured epoxies and polyurethanes. In some cases, these materials can even be applied to surfaces already underwater. Such a water curing epoxy is the preferred embodiment of the current invention.

The coatings described herein may not include ablative materials. The inner polymer layer 99, though it may contain copper in many various forms, can be covered by the outer polymer layer 98 without impeding the functioning of the inner polymer layer 99, as the functioning of the two layers are completely independent of each other. The inner polymer layer's active chemical compounds, including cupro-metallic compounds, salts, and alloys do not function by leaching compounds into the water. The repulsion of the biofouling animal organisms by the active chemical compounds in the outer polymer layer 98 protects the integrity of the outer polymer layer 98, which in turn protects the integrity of the inner polymer layer 99 and the entire coating itself, and in turn protects the coated protected submerged surface structure.

Thus, two layered polymer paint coatings may help to protect both freshwater and seawater submerged surface structures and their protective coatings from disruption, discoloration, corrosion, damage, and deterioration resulting from chemical, ultraviolet, galvanic, and proliferative biological processes initiated in the water. The chemical activity of the compounds in the coatings has a primary function to protect each layer of the protective polymer coating and the protected submerged surface structure underneath from damage, discoloration, and deterioration that would result from uncontrolled bio-proliferative processes attacking the coating, with such damage in turn leading to further damage from chemical, corrosive, and galvanic attack from the surrounding water. The two polymer layers of the coating provide long-term protection from these same processes, insuring that the coating may have at least a ten-year operational life. The polymer used in the outer polymer layer 98 may be, as previously stated, either a polyurethane (PUR) or a fluorourethane (FUR), which provides ultraviolet light protection and mechanical durability and resistance to frictional and abrasive mechanical processes to the coating as well and the flexibility of PUR and FUR polymer coatings allow for a self-sealing property to be conferred to the coating thereby allowing self-repair of small defects in the coating that might be caused by attempted settlement of a juvenile barnacle or small collisions from debris in the water. Note that any of numerous varieties and classes of PUR's and FUR's may be used, based upon application and economic requirements and restrictions. Also, millions of different pigment hues and colors may be added to the outer polymer layer 98 for cosmetic purposes.

Bio-proliferative processes need not always involve living macro-biofouling animal organisms, such as barnacles, invasive mussels, marine borers (ship worms), tunicates, and tube worms. For instance, one such process deposits slime, that is a complex network matrix of protein laid down on the coating surface, and begins as soon as the surface is submerged in water. This can happen even without any macro-biofouling animal or plant organisms, and can be the result of microscopic biological activity. Scale deposits of calcium or magnesium carbonate can attach themselves if the water is saturated in these materials, or if the original occupiers of old shells leave their skeleton shells behind to precipitate more carbonate deposits into the water, or for that matter, provide new places for settlement of future biofouling animal organisms.

However, the extremely smooth low friction surfaces of PUR and especially FUR as compared to typical ablative paint coatings make it more difficult for these problems associated with scale to accumulate, any slime deposits would be removed even when the boat moved at low velocities, and the chemically active agents in the outer polymer layer would prevent any sizeable accumulation of a scum later from building up. Powdered PTFE (Teflon-®) or various silicone and siloxane additives can be added to the PUR or FUR of the outer polymer layer to facilitate even further the shedding of the bioslime layer from the hull at even the slowest of velocities of the boat through the water.

These additives, by reducing the coefficient of friction as well when the boat is moving at high velocities, greatly improve the performance of the boat in terms of speed for a given consumption of fuel and boat design. The combination of the biochemically active surface property of the outer polymer coating of this invention combined with these means to produce minimal friction on water movement by the outer polymer layer will allow the ship's hull to remain immersed in stagnant water in a harbor for very long periods of time without any more bio-proliferative accumulation on the hull than what would be accumulated if that protected surface structure was moving significantly (greater than 10 mph) with respect to the water. If a ship was to remain in stagnant water and unused for a period of months, gentle wiping of any bioslime layer that might accumulate with a cloth would greatly add to the cosmetic appearance of the boat and make it less likely that any accumulated bioslime would allow algae to take a foot hole on the hull, which might prevent other biofouling organisms from making contact with the chemically active substances on the surface of the outer polymer layer designed to repel them off the surface. Note that if a boat painted with a self-polishing soft ablative copper paint is in stagnant water and not used for a long period of time, the paint will work improperly, because there would be no moving water to wash away the decomposed paint matrix and therefore, the antifouling effect of the paint as it discharged its chemically active substances into the water while remaining stationary would be inconsistent and unreliable; effective use of soft ablative paint coatings would require significant motion of the boat relative to the water.

The inner polymer layer 99 may be impregnated with a water insoluble cupro-metallic salt, such as cuprous oxide, a cupro-metallic alloy, such as copper-zinc-tin at the weight percentage specifications described above, or elemental copper. These materials may function to keep the inner polymer layer 99 intact from disruption, deterioration, corrosion, and damage in the unlikely event that any of the chemical, ultraviolet, galvanic, and proliferative biological processes that are initiated in and from the surrounding water break through the outer polymer paint layer 98 to the inner layer 99. Any cupro-metallic salt may be used for this purpose, including both water-insoluble and water-soluble substances, as well as innumerable other active chemical substances that can slow bio-proliferative processes. Pure copper may be used in the form of >99% purity powder or flakes.

The polymer used in the inner polymer layer 99 may be an epoxy which provides tight adhesion to the protected surface and which is compatible with most cupro-metallic additive substances. The epoxy can be applied underwater to a surface to be protected that is already submerged. The cuprous oxide material helps to ensure that the inner polymer layer 99 will remain completely intact, without corrosion, damage and deterioration from these water initiated bio-proliferative associated processes. This, in turn, keeps the submerged surface underneath the inner polymer layer 99 protected from and completely free of corrosion, damage, disruption, and deterioration from these chemical, ultraviolet, galvanic, and proliferative biological processes that are initiated in the water surrounding the protected surface. This physical protective interaction between the two polymer paint layers, produced by the presence of the different specified ingredients impregnating the two polymer paint layers of the polymer coating, is responsible for protecting the submerged surface covered by that coating. The interlocking protections of the two polymer paint layers maintain help to achieve a long operational life and protection of the underlying submerged surface.

As already explained in this disclosure, the outer polymer layer 98 serves also to protect and shield the aquatic environment from exposure to the cupro-metallic salt, in this preferred case, cuprous oxide, or any other potent chemically active substances in the inner polymer layer 99. There is no leaching of the cuprous oxide salt into the aquatic environment, nor is there any macroscopic chemical reaction with the cuprous oxide salt with the surrounding seawater to produce copper hydroxychloride, which would otherwise be deposited in the aquatic environment. Any of the antifouling agents described herein may be used in the inner polymer layer 99 with the protection of the outer polymer layer 98, and there would be no harmful effects on the environment.

Even the various cupro-metallic alloys may be used in the inner polymer layer 99, although the increased stability of the cupro-metallic alloy makes it preferable to be used in the outer polymer layer 98, where it is well tolerated in the aquatic environment. One can compensate for the increased stability of the cupro-metallic alloys by using them at a much higher percentage by weight composition in the inner polymer layer 99 than in the outer polymer layer 98.

Thus, the only limitation on what biocidally active compounds can be used in the inner polymer layer 99 relate to the chemical and physical compatibility of the compounds with the polymer epoxy making up the inner polymer layer 99, as well as the biologically and chemically active chemical substances impregnating that inner polymer layer 99, and the physical and chemical compatibility with the material making up the protected submerged surface structure. Should there be any incompatibility between the active chemical compounds in the inner polymer layer 99 and the material comprising the submerged protected surface structure, an inner polymer primer layer can be placed between the inner polymer layer and the protected surface.

An example of this incompatibility is the inadvisability of applying the inner polymer layer with a cupro-metallic substance directly on an aluminum boat hull, because of the potential for galvanic interaction between the more chemically active aluminum in the boat hull and the more chemically noble, less chemically active copper in the inner polymer layer. The one notable exception is cuprous thiocyanate which can be used on both aluminum and steel hulls and its previously noted intense white color is useful as mentioned when a white color to a ship's hull is desired. In that case, an inner polymer primer layer may be used, formed from any appropriate polymer material, even the same epoxy material as in the inner polymer layer, but without being impregnated with any of the biologically active compounds used in the inner polymer layer. As seen in FIG. 1 , the primer layer 104 may be placed upon the protected surface 105 before the inner polymer layer.

Even though the epoxy in the inner polymer layer may be formulated to be compatible with either the fluorourethane or polyurethane outer polymer layer to be coated upon it, nevertheless, it is possible that one of the biochemically active substances in the inner polymer layer might be chemically or physically incompatible with one of the biochemically active substances in the outer polymer layer. This problem can be remedied as seen in FIG. 1 , with an additional outer primer layer of the epoxy 103, without any chemically active compounds, placed between the inner polymer layer 99 and the outer polymer layer 98.

While the use of cupro-metallic metal, alloys, and salts in inner layer 99 have been described in detail, other heavy metals salts including zinc oxide, titanium oxide, oxides of iron, silver oxide, and similar such materials, can also be used. It is important to note that, while zinc oxide by itself has only a weak effect on biofouling animal organisms, it has been shown to synergistically enhance the biofouling anti-proliferating effect of copper and its alloys and salts by up to 200 times when used in combination with the copper containing-substance. For this reason zinc oxide is especially useful in combination with cuprous oxide.

Zinc oxide forms a similar compound with seawater, zinc hydroxy-chloride (Zn₂(OH)₃Cl) that performs the same functions as previously described for copper hydroxy-chloride, namely a juvenile barnacle anti-proliferating effect and a sealing effect within the inner polymer layer 99. Again the outer polymer layer 98 covering the inner polymer layer 98 prevents any leaching out of the Zn ions into the environment, which like copper ions are detrimental, though to a lesser extent than the copper ions. The other heavy metal oxides, such as those listed above, would be expected to behave chemically very similar to the zinc oxide.

Another feature of this invention is that, after several years of the coating having been in use, there may be some degradation of the coating, in particular the outside polymer layer. This degradation may occur because of wear and tear, collisions with debris in the water, or an unexpected large number of barnacles, mussels, and other types of biofouling animal organisms in their juvenile forms that had tried to settle on the coating leaving microscopic defects that all might have changed the functional and cosmetic features of this coating. However, the coating can be easily augmented without removal of the existing coating. The process is simply to lightly sandpaper the existing outer polymer layer 98, clean the surface off with water, let dry, and then apply over the old polymer layer 98 a new outer polymer layer 98 with the same impregnated chemically active agents. If technology has advanced with respect to the means of preventing damage, deterioration, or discoloration caused by bio-proliferative processes to the protected surface and structure, the new outer polymer layer can contain a different selection of chemically active agents used for this purpose. The remnants of the old outer polymer layer remain and still contribute to the protection of the surface structure.

One can also use the replacement outer polymer layer 98 only on limited areas of the protective coating if, for the most part, most of the coating remains in excellent condition. This repair to the coating is a simple task of placing a layer of PUR or FUR on a previously applied layer of PUR or FUR. In comparison, materials such as polyester gelcoats are notoriously difficult to work with, for example when trying to repair a fiberglass hull. An embodiment of this invention making use of this situation will be described later in detail as an application of the present coating invention.

Also, if the outer polymer layer 98 is comprised of PUR, and the protected structural surface is a moving structural surface like a boat, at the owner's discretion to gain additional performance operating specifications, a previously existing outer polymer layer 98 of PUR with chemically active substances can either be replaced by a new polymer layer 98 comprised of FUR with the same or a different new selection of impregnated chemically active substances, or this new layer can be simply painted over the old outer polymer layer with just the simple surface preparation with sandpaper just described. In all of these cases, it is important to note that the inner polymer layer that contains the potentially environmentally harmful chemically active substances would not be touched, would not be required to be disposed of in a landfill or some other location, until the boat itself is retired from operation. Indeed this coating arrangement, if used as a bottom hull boat paint would last the lifetime of the boat, especially given that outer polymer layer 99 replacement would be quite infrequent and only after collision type damage to the boat or some other type of unusual mechanical damage to the coating given that the operating lifetimes of the PUR type of external outer polymer layer, and especially the FUR type of external outer polymer layer, is so dramatically long.

The non-ablative nature of each of the layers, including the two layered coating, provides some additional benefits. First, ablative paint coatings use very high concentrations of the chemically active agent because of the very high leach rate of the chemically active agent into the surrounding water that is required to accomplish its function of eliminating biofouling larval animal organisms in the water. For example, in the case of a copper salt, that weight concentration can be as high as 70% by weight of the coating, which adds considerably to costs.

With non-ablative coatings, however, because there is no significant leaching of the chemically active substance into the surrounding water, the concentration of copper chemically active substances can be around 10%. Also, whereas the copper ablative coating exhausts its supply of chemically active substance quickly, within the space of only one to two seasons, necessitating its removal, its disposal in an environmentally safe manner, and its replacement by a new coating, the coating of this invention will never exhaust its supply of chemically active compounds in the inner polymer layer 99 or the Cu Zn Sn alloy powder in the outer polymer coating 98 and can maintain its high level of antifouling activity for the many years that the coating's lifetime is expected to be operational.

Second, if a boat sits stationary for several weeks in the water without being used, it will develop a bioslime on the outside of the hull. Whether the coating is ablative or not ablative, if the boat does not move often in the water, moving water will not wash off the biofilm, which can accumulate to the point of unsightly cosmetic appearance, and can interfere with the antifouling function of the surface of the coating facing the water because now the coating's surface will have more nutrients to attract antifouling larval lifeforms. The biofilm might further prevent the organisms from touching or contacting the chemically active substance within the coating that would normally inhibit their settlement. Thus, a boat immobile in a harbor for several weeks must have its hull be wiped down, necessitating underwater divers to do this work periodically. If that must be done, some jurisdictions require the boat to be removed from the harbor when cleaned in this manner. because a wiping of an ablative coating can remove up to one third of the chemically active substance quickly by the wiping, depositing it into the harbor. This problem does not occur with the non-ablative nature of the coatings described herein. Wiping a hull with the present coatings will not release any of the chemically active substances in outer polymer layer 98 into the surrounding water.

Third, such a wiping of biofilm as described above may simply move live biofilm organisms (bacteria, fungi, single cell algae) from one part of the water to another to be again deposited on the boat, where they will immediately grow again. To prevent that from happening, the boat can be gently wiped down with wipes that contain standard household disinfectants, such as quaternary ammonium disinfectants which will inactivate the organisms comprising the biofilm so that they will not resettle elsewhere on the hull. Disinfectants such as these can even be added to the outside polymer layer of this invention as one of the chemically active substances to inhibit further the development of biofilms. Disinfectants such as these can be problematical with ablative paints, as they can react with the ablative paint matrix or the chemically active substances contained within them or both.

The coatings described herein may have a variety of applications. All of the following application embodiments have all of the surface structure protection features and aquatic environmental safety features described herein.

A first application is a hull boat bottom paint. As a hull boat bottom paint, a boat may be painted once or twice in the lifetime of the operating life of the boat, depending upon whether FUR or PUR respectively is used in the hull bottom paint. If damaged, the outer polymer layer 98 can be replaced in its entirety or in just a portion of the hull surface with a new outer polymer layer 98. Since no soft ablative paint or especially hard ablative paint is involved in this coating, the boat owner does not have to engage in expensive hull painting, stripping of the old ablative paint and coating remnants with replacement of a new ablative paint coating, every one to two years. Avoiding such repainting provides a reduction in the amount of hazardous waste that is generated. Without any accidental collision damage, and with proper light cleaning periodically every several weeks if the boat spends long times in stagnant water, a boat may never need repainting once the hull bottom paint coating described herein is applied. If the outer polymer layer 98 includes PUR, then a coating replacement may be needed every 5 or 8 to 10 years, which would involve only the outer polymer layer 98; if the outer polymer layer includes FUR, a coating replacement may be needed up to every 25 years. The inner polymer layer 99 with the more potent chemically active substances that can present a problem in terms of environmental disposal would never have to be replaced.

By using a chemically active substance in the inner polymer layer, called cuprous thiocyanate, because of its lack of galvanic activity with aluminum hulls, and because of its intense white color, one can paint aluminum hulls a cosmetically pleasing brilliant white color without additional white pigment being added, even though this material is a copper salt which generally gives a pink color to hull paint to which pigment has not been added.

Another application is a gelcoat applied to a newly manufactured fiberglass boat. In some cases, a boat may be manufactured by the following process: A female mold of the hull is coated with a mold release and a female mold of the cabin is coated with a mold release. A gelcoat of polyester resin polymer is applied next and is the first layer of the hull and is the layer that faces out to and contacts the water. Because the polyester gelcoat is porous to water, a layer of water impermeable epoxy is applied next. Then the hull of the boat (as well as the cabin half) has layers of fiberglass net sheeting and more epoxy applied to build up the thickness of the hull and cabin. When both achieve the proper thickness, the cabin is released from the mold, suspended, and gently brought down upon the hull, where it is attached to the hull and glued into one unit comprising the fiberglass boat. After final curing, the hull is released from the mold, and the newly manufactured boat is buffed up, polished, excess wax from the gelcoat curing process and any residual mold release agent is removed with the hull being checked for any defects which are repaired. The boat is then packaged off to a vendor to sell to the public.

This manufacturing process may be altered to accommodate the processes described herein. First the problematical polyester gelcoat, problematical because it is so easily damaged and water permeable, is replaced and no longer used. Instead of the polyester gelcoat, the inner polymer layer 99 of the present invention with its impregnated chemically active agents described herein, including all forms of cupro-metallic based substances, may be used as the first layer applied in the hull mold, the layer that will face and contact the water. It is used with a mold release agent compatible with an epoxy, rather than a polyester gelcoat, and there are several such releasing agents available. The hull and the cabin rest of the boat may then be assembled. After the final layer of fiberglass and epoxy has cured, the boat is released from the hull mold, all wax and residual releasing agent are removed, and the surface is buffed with fine sandpaper. As the next step, the outer polymer layer 98, which may include FUR or PUR with its pertinent impregnated chemically active agents, is applied to the inner polymer layer 99 that now forms the outer layer of the boat hull. The FUR or PUR, with its pertinent impregnated chemically active agents, as well as the desired pigment for the required hull color and anti-friction additives such as PTFE, is now the new “gelcoat.” The boat hull, now “gelcoated” as described herein, has extremely high pigment and gloss retention that can last from 5 to 8 years for PUR or up to 25 years for FUR.

All of the other problems of polyester gelcoat, especially repairing damage to polyester gelcoat coatings and putting a new layer of gelcoat over an old layer of gelcoat, are eliminated. The PUR/FUR gelcoat has all of the durability, scratch resistance, and gloss of the old polyester gelcoat. The long operating lifetime of such coatings more than makes up for any increased cost.

As a last step, the coating surface of the boat hull and the rest of the boat may be finely sanded, buffed, and polished. Aside from augmenting the boat's cosmetic appearance, the final buffing and polishing exposes on the surface more of the particles of the chemically active substances impregnated within it, thereby enhancing the protective activity of the new outer polymer layer PUR/FUR 98 gelcoat as soon as it is placed in the water. Essentially, the boat comes off the assembly line with the elements comprising this invention as integral elements of the boat hull itself. The hull is pre-reinforced against damage, deterioration, and discoloration from chemical, radiant, galvanic, and bio-proliferative processes originating in the surrounding water before it is sold to the consumer.

The boat will have the appearance, gloss and any desired color that a newly manufactured car has, with a coating that will last as long as any manufactured car has. Automotive coatings may use polyurethanes to achieve their fantastic results via an inner PUR base coat and outer PUR clear coat of the acrylic PUR kind, while virtually none will use the even more durable fluorourethanes. In contrast, new boats cannot compete in appearance with the paint job of a newly manufactured car. The boat coating described herein, with the PUR or FUR outer gelcoat polymer layer 98 and inner polymer layer 99, will afford superior appearance to the boat equal to that of a newly manufactured car, and with built in protection of the hull structure against bio-proliferative processes even before the owner ever takes possession of the boat.

The owner will never have to paint the boat for many years, and if a FUR coating is used, perhaps never if there is no collision damage that would occur during the operating lifetime of the boat. The decision to use the superior but more expensive FUR coating over that of PUR coating is determined by both economic factors and the use of the boat in terms of whether it would be a simple leisure boat versus a high performance racing boat.

A third application is a coating to be applied to a boat propeller, which can be applied at the time of manufacture or by the user subsequent to its installation on a ship or boat. Ship and boat propellers may be made from either metal, such as stainless steel, aluminum, brass, bronze, titanium, copper aluminum alloys or other types of metal alloys, or they may be made of ceramics. In protecting propellers and their surfaces from all of the processes that the current invention are effective against, especially bio-proliferative processes, the coating has to withstand tremendous centrifugal and frictional forces and cavitation air bubbles, especially at the propeller edges. Thus, the coating should have as high an adhesion to the propeller surface as possible. Some available coatings last only one season.

Propellor coatings sometimes include a zinc chromate yellow primer, which is extremely carcinogenic, quite dangerous to the applicator (often a lay consumer), and is in the process of being banned or highly limited in use in various jurisdictions. The zinc chromate layer is covered by a silicone polymer that reduces friction between the water and the propeller blade. It relies on low friction conditions to prevent the bio-proliferation via attachment and growth of biofouling animal organisms.

However, that outer layer has no chemically active substances for preventing bio-proliferative processes and relies solely on the low friction of the moving water against the outside coating layer of the propeller blade, so when the ship and propeller stay still in stagnant water for any significant length of time, biofouling animal organisms can easily go through the outer low friction polymer layer and grow into the inner zinc chromate layer where they can be eradicated by the zinc chromate. However, this coating will leach dangerous chromate ions into the aquatic environment, especially at the end of the first or second season when progressive damage to the outer low friction layer begins to expose significant amounts of the propeller and its dangerous zinc chromate coating to the aquatic environment with rapidly increasing amounts of chromate contamination occurring until the coating is removed and replaced with a newer coating.

Such coatings are furthermore exceptionally expensive, costing thousands of dollars a gallon. To apply them, one has to first white sandblast the propeller and its old paint down to the bare white metal, which in of itself produces unfavorable environmental contamination if the residues and aerosols produced by this process are not properly handled and disposed of as well as medical dangers of cancer, chromate injury, and lung injury to people who often do not take the proper precautions. The zinc chromate acts as a primer, allowing good attachment of the outer low friction layer to the propeller surface; its function is not to eradicate bio-proliferative processes, but it does eradicate some biofouling animal organisms because of the severe toxicity of zinc chromate to all animal life. Note that unlike the outer polymer layer 98 of the current invention shielding the inner polymer layer 99 with potent chemically active substances from the surrounding water, the outer low friction layer in the zinc chromate current art system does little to no shielding of the toxic zinc chromate from the surrounding toxic environment, because it soon begins to wear off.

Some boat owners enjoy the cosmetic appearance of having the barnacles falling off the propeller, not realizing that that is occurring because of the zinc chromate being directly exposed to the aquatic environment, even as the coating is eradicating some of the barnacles. The coating eventually fails, because not all the mature barnacles fall off, some are slowly poisoned by the zinc chromate while they attain adulthood and large size, and they become the nidus for new barnacles to easily attach as well as greatly and harmfully increasing friction on the propeller blade. Even one mature barnacle on a propeller blade will increase fuel consumption, increase vibration and cavitation, and shorten the life of the propeller via corrosion and increase mechanical water turbulence, possibly even damaging the engine through excessive vibration.

Other representatives of the current art include coatings consisting of zinc spray in a polymer and hull ablative paints which are ineffective in preventing larval forms and juvenile forms of the biofouling animal organism from progressing into adult biofouling organisms—barnacles and mussels, which then subsequently at its worst, damage the propeller blades and shaft, or at its best, requires a difficult removal of the barnacles and mussels, as well as the old damaged paint and repair to the areas of chemical and biological corrosion that occurred because of the bio-proliferation. Such bio-proliferation is responsible for greatly increased friction of the propeller with the water, greatly increasing fuel consumption and cost, as well as creating disturbances and vibrations in what should be smooth flow and rotation of the blades leading to possible engine damage.

Propellers may be coated with a process that eliminates all of the above problems. Besides being cheaper by an order of magnitude, the coatings described herein are not carcinogenic unless grossly misused or mishandled. The process of using such a coating is as follows: The propeller is simply sanded by hand or with an electric sander to the point that all loose paint, rust, grease, and debris are removed, the blades are cleaned with a solvent, and no sandblasting is required. A first layer of the coating may then be applied to the propeller blades and shaft, such as an extremely adhesive epoxy (2,500 PSI) without any chemically active substances. This highly adherent epoxy primer layer 104 of FIG. 1 , may be selected to provide strong adhesion of the coating onto the metal or ceramic surface of the propeller and can cure in the presence of water. Zinc or aluminum powder may be added to the epoxy primer if desired to produce a zinc rich or aluminum rich primer for steel propellers.

Next, inner polymer layer 99 with a cupro-metallic substance or substances is applied as the second mid-coat layer on top of the inner primer layer 104. Finally, outer polymer layer 98 of a FUR polymer impregnated with PTFE powder, any desired pigment, and a combination of nonivamide, Cu Zn Sn alloy powder, zinc pyrithione, and with or without medetomidine may be coated as a topcoat over the mid-coat inner polymer layer 99.

The outer polymer layer 98 may include a fluorourethane (FUR) for maximum durability, wear, abrasion, low friction, water and chemical imperviousness to withstand the severe water rotational forces and cavitary bubble disturbances around the whirling propeller blades. This three-layer process may have at least a 5 year operational lifespan, as opposed to the one or two seasons with the zinc chromate system. The fluorourethane polymer protects a propeller apparatus from not only bio-proliferative processes, but also radiant, chemical, galvanic, and mechanical abrasive processes originating in the surrounding water as well.

A fourth important application includes a coating to be applied to structures of a marina. There are three principal structural components to a marina that services boats and ships. First, steel bulkheads often line the perimeter of the marina. Second, pylons made out of wood or concrete to which docks and piers are at attached, if the docks and piers are not floating. Third, floating piers and docks, which rise and fall with the tide, that rest on floats largely made of ultrahigh molecular weight polyethylene plastic (UHMWPE). All three components are subject to bio-proliferative biofouling processes as well as chemical and galvanic processes, and they all need to be protected in some manner to prevent expensive damage requiring eventual replacement.

With respect to steel bulkheads, they are subject to severe corrosion via chemical and galvanic interaction with water, especially seawater. Because the iron in the steel bulkhead is moderately toxic to biofouling animal organisms that try to settle there, the biological proliferations are not usually as severe as on other submerged surfaces, but do remain a factor. The iron in the steel plates is attacked by both the chlorine ion and oxygen in saltwater, and hydrogen and oxygen in freshwater. Even when measures are taken to inhibit these processes, steel bulkheads often have to be replaced every several years, at a significant cost. At least part of the bulkheads are constantly wet, which limits the coating options that can be used. Normally the bulkhead steel plates come coated with an iron oxide primer as their only protection, which shortly corrodes. The coatings described herein may be used to preserve these structures.

Three layers of polymer may be used to coat steel bulkheads. The first inner layer may be a high adhesion epoxy polymer system used as an inner primer layer 104 that is capable of curing in the presence of water. This epoxy system may be free of any copper or other chemically active substances to avoid galvanic action between the steel bulkhead and cupro-metallic substances. Zinc or aluminum powder may be added to the inner primer layer 104 to further hinder any chemical corrosion of the bulkhead. Next a mid-coat of inner polymer layer 99 with a cupro-metallic chemically active substance impregnating a layer of the same moisture-tolerant epoxy polymer system may be laid down. Third, a top coat comprising outer polyurethane (PUR) outer polymer layer 98 may be laid down, in which a tin-brass alloy powder, nonivamide powder, and zinc pyrithione (ZPT) are impregnated, thus completing the coating. This triple coating will prevent damage, deterioration, and discoloration, for example in the form of rust disintegration caused by chemical, galvanic, radiant, and bio-proliferative processes emanating from the water.

This coating may be used instead of an iron oxide coating primer placed on the bulkhead plates at the time of manufacture, or this coating can be placed on top of such a primer to make a four layer coating. Fluorourethane, because of its cost, may be omitted in favor of PUR and the PTFE and pigment which can be used in the outer polymer layer 98 can be omitted. The PUR and the FUR shields the UV sensitive epoxy polymer from UV damage.

The wood components of the marina, including docks, piers and so forth, may be treated with an inner polymer layer 99 of the epoxy system, impregnated with a chemically active substance such as a cupro-metallic substance. The epoxy may be prepared above the surface of the water and applied to underwater portions of these structures, and may be allowed to cure underwater, preferably best done at lowest tide. Both wood and concrete pylons anchoring docks and piers in the marina can be treated in the same way. On top of the inner polymer 99, a polyurethane coat outer polymer layer containing the same chemically active substances as described under the bulkhead coating may be used.

The chemicals normally put into marina wood structures to act as preservatives, such as arsenical compounds (copper chromium arsenate—now no longer put into wood as of 2004) or copper chromium compounds, which are toxic to many aquatic life forms and which normally would constantly leak into the water of the marina, can be eliminated. Such treated wood (also known as pressure treated wood) would be replaced by the coating of this embodiment. The coating may be put on at the time of manufacture. Optionally a wood sealant could be used prior to the application of the coating of this embodiment.

The coating would be capable of eradicating marine shipworms (e.g., marine ship borers) which cause millions of dollars of damage to wooden marina structures annually. In freshwater, the coating would be able to halt proliferation and attachment of bio-proliferating invasive mussels (quagga and zebra types), which are a major source of damage to all marina structures, especially wood structures in freshwater. In warm and tropical areas, the damage done to marina structures by barnacles in marine environments is enormous and this problem can be greatly ameliorated by using such a coating.

The bio-proliferation of biofouling animal organisms and plant organisms on floating plastic UHMWPE float structures in marinas is a further challenge. These include structures like dock and pier floats, bumper guards for boats and so forth. One particular problem manifested by these structures is that, while they are not subject to galvanic and chemical processes, they will be harmed by radiant UV processes that produce caulking and cracking, and bio-proliferating processes of biofouling animal and plant organisms that have the remarkable ability to stick to the low friction surface of UHMWPE plastic and invade even that material.

To complicate matters further, it is virtually impossible to paint or coat UHMWPE plastic surfaces because of its low surface tension. However, with the recent availability of adhesion promoters that are effective with this plastic, coatings may be applied on these plastic structures preferentially at the time of manufacture, or when they are installed in the field. An embodiment that would accomplish the protection from water from chemical, radiant, and bio-proliferative damage (galvanic processes do not apply here) calls for cleaning the surface of the float to be submerged with water and solvents to remove all dirt, grease, and oil. Next the UHMWPE float surface is sprayed with a proper adhesion promoter followed by an epoxy system inner polymer layer 99 containing cupro-metallic or other chemically active substances, followed by an outer polymer layer 98 containing nonivamide, CuZnSn tin brass powder, and ZPT.

A fifth application is a coating to be applied structures known as wave energy converters, which may be used to harvest wave energy and transform it to electrical energy. There are several different types of wave energy converter (WEC) systems that all have some moving parts to their mechanical systems. They all have three problems in common—1) If barnacles or mussels proliferate on the moving parts, they will be destroyed; 2) If biofouling animal organisms proliferate in large quantities, especially true also of Sea Grapes, the increased weight of these organisms will sink these structures, again destroying it; and 3) Barnacles in marine environments and invasive mussels in freshwater environments will attach, and if the WEC is not destroyed by them, the greatly increased friction produced by these biofouling animal organisms will interfere with WEC generator motion, slow it down, and decrease the electric power that is generated, reducing the efficiency of the entire system.

Taking one specific wave energy converter (WEC) system as an example, a device known as an omnidirectional wave energy point absorber, this is a device that moves a set of magnets in a vertical direction through a set of coils as a passing wave moves a float in a vertical sinusoidal manner in response to the wave motion and this vertical wave motion is transferred to the magnets in the WEC by a vertically moving coil attached to the magnets. As the magnets move relative to the stationary coils, the mechanical energy of the waves is converted into electrical energy, which is then used or stored. This system has parts made of several types of materials. The materials of moving and external parts of the device may include carbon fiber plastic, polycarbonate plastic, and stainless steel alloys of various types. These surfaces of different materials are vulnerable to bio-proliferating life forms that will destroy the WEC device or, at the least, interfere with its operation. The polycarbonate also needs to be provided with UV protection as well.

To protect such a WEC, the plastic and carbon fiber outward-facing parts that touch the surrounding water and moving parts may be coated in two layers. An outer polymer coating 98 may include nonivamide, CuZnSn tin brass powder, and zinc pyrithione impregnated into a layer of fluorourethane. This coating may be applied to an inner polymer layer 99 of an epoxy polymer with high adhesion characteristics and moisture tolerance, that has cupro-metallic substances impregnated into it. Other chemically active substances as may also be used. Stainless steel and any other metal moving part or externally facing part in contact with the surrounding water may be coated in the same manner as the plastic and carbon fiber components of the WEC, for example using the same outer polymer layer 98 with the same impregnated chemically active substances, and the same inner polymer layer 99 with the same chemically active substances.

In addition to these two layers, the inner polymer layer 99 may be coated onto an inner primer layer 104 of the same extremely adherent epoxy polymer that contains no chemically active substances. Because the WEC is operating under such severe conditions, the coating should be extremely durable and tough and provide heavy UV protection to the exposed parts of the device. For that reason, FUR may be used in the outer polymer layer 98 on any exposed surface, especially because of its exceptionally high UV resistance and absorption. The triple layered coat, because it is so adherent and tough, may be used on all exposed or moving parts of a critical or moving nature. The use of this coating eliminates the need for the toxic zinc chromate primer.

In addition, because of the close presence of intense magnetic and electric fields generated from the powerful magnets interacting with copper coils within the WEC, the coating should be completely non-magnetic and non-conductive electrically. The impregnated chemically active substances into the two upper layers of the coating, inner polymer layer 99 and outer polymer layer 98, are suitable for this. In particular, the concentration of tin-brass alloy powder may not exceed 10% to avoid the outer polymer layer 98 from becoming electrically conductive. If pure metal copper or cupro-metallic alloys are used in the inner polymer layer 99, the concentration should not exceed 10% to avoid that layer from having electrically conductive properties. Cupro-metallic salts are not conductive, so conductivity will not be of concern if cupro-metallic salts are used only in the inner polymer layer 99. If either layer were magnetic or electrically conductive, undesirable magnetic fields and electrical currents could arise within the coating layers that would interfere with the operation of the generator, reduce the power output, and could reduce the operating life of the coating.

In addition to WEC buoys that to produce power from waves, the properties of the coating of the current invention can protect the external surfaces of buoys used for other purposes. These additional uses include buoys that carry weather, ocean, or atmosphere measuring instrumentation as well as those buoys that are used for navigational purposes.

Any of the embodiments described herein, which may include a two layer polymer coating system, as well as any other embodiments derived from them, be used for the protection of the following non-all-inclusive list of submerged structures: boat hulls, boat propellers, gelcoats for newly manufactured boats, marina piers and docks, water and electric power intake and outflow pipes, bulkheads and bulwarks, navigational lock structures, boat ballast tank and system structures, bridge pylons, off-shore drilling rigs, water-submerged concrete structures of any kind, naval and commercial boat hulls and their internal plumbing systems (excluding those systems used for water transport for drinking and bathing), seawater- or freshwater-cooled boat engine cooling systems including heat exchangers, piping and engine blocks, ocean wave energy converters, undersea electrical cables, undersea piping systems, navigational and instrument buoys, floating fishing platforms, canal locks, and submarines.

Some boat owners demand a boat with a white hull and no colored or hued paint of any shade other than pure white. Some formulations of the two layer coating can be used to provide such a white coating. First, the inner polymer layer, instead of containing only cuprous oxide which would otherwise give the inner polymer layer a pinkish hue, the cuprous oxide can be either partly or fully substituted with the copper salt, cuprous thiocyanate, which functions in the same manner as described for the cuprous oxide, but that has a pure bright white color. It can either replace the cuprous oxide completely, or allow the cuprous oxide to be used in a smaller concentration by weight, thereby eliminating the pinkish hue that the cuprous oxide gives the inner polymer layer.

Second, in the outer polymer layer, the Cu Zn Sn powder may also give the coating a pinkish hue. Three things, however, can be done to give that layer an opaque pure white color: 1) Titanium dioxide (TiO₂), a pure white substance often used as a white pigment in paints, can be added to the outer layer in high concentrations, between 10 and 40% by weight of the coating, to offset the pinkish hue from the copper alloy powder; 2) Because the TiO₂ is unstable with exposure to UV light and this could corrupt the durability of the coating via oxygen radical formation, it must be shielded from the UV; for this reason, the outer polymer layer may e a flourourethane, which will not let UV photons pass through to the TiO₂ in the outer polymer layer; and 3) The particles of Cu Zn Sn alloy may be made much smaller than the 44 microns described above, with a desirable range in the 75 to 150 nm range, so that the average particle size is much less than the half wave length of red light (620-750 nm), thereby making the particles of the alloy tin brass powder transparent to red light and eliminating the source of the pink hue in the outer polymer layer. These modifications would produce the brilliant pure white color demanded by some boat owners because the pinkish hue would be eliminated from both polymer layers of the coating.

In all of these applications, the specified ingredients impregnated into the two layered coating system, at their designated respective locations within the two polymer layers of the coating, protect this paint coating from corrosion, damage, deterioration, and discoloration from chemical, ultraviolet, proliferative biological, and galvanic processes originating from and within the surrounding water. In providing this protection to the integrity of the coating, these specified materials, impregnated within different layers of the two layer paint polymer coating system, shield and protect metal and non-metal submerged surface structures from these same galvanic, chemical, ultraviolet, and biological processes initiating in and from the surrounding water. These sequential protective processes of, first, protecting the polymer paint coating by having the outer polymer layer protect the inner polymer layer, and, second, the resulting two layer coating complex consequently protecting the submerged surface structure, results in a prolonged operational life and integrity of both the polymer paint coating system and the protected submerged surface structure upon which it is coated.

Any chemical substance that is insoluble in water, or if somewhat water soluble, is at least held tightly bound to the outer polymer matrix, that has activity against chemical and biological proliferative processes originating in the surrounding water, that has both physical and chemical compatibility with the polymer comprising the outer polymer layer 98 and its other impregnated chemical substances, that will protect the inner polymer layer from damage, deterioration, and corrosion from such chemical and proliferative biological processes and is also compatible with the polymer and impregnated chemical substance of the inner polymer layer, and is also not harmful to the surrounding aquatic environment, is appropriate for use in the outer polymer layer. While the list of possible chemical substances that was mentioned in this disclosure is very extensive, the list should not be interpreted as being exclusive of other potential substances. Any substance is suitable for use in the outer polymer layer of this invention may be so used. Any chemical substance that has both physical and chemical compatibility with the polymer comprising the inner polymer layer, and any of the biologically and chemically active substances impregnated into it and the material comprising the protected submerged surface structure underneath the inner polymer layer, and that is capable of protecting the underlying submerged surface structure, is appropriate for use in the inner polymer layer to prevent damage, deterioration, discoloration, and corrosion of the protected surface structure underneath. While the list of possible chemical substances that was mentioned in this disclosure as appropriate for use in the inner polymer layer is very extensive, the list should not be interpreted as being exclusive of other potential substances. Any substance that is suitable for use in the inner polymer layer can be so used.

With respect to the inner polymer layer 99, the range of possible impregnated substances that would have the ability to eradicate any juvenile biofouling animal organisms is much broader. The only limitations on this class of chemically active substances would be any such substance that is not physically or chemically compatible with either the inner layer polymer or other impregnated chemically active substances within that inner polymer layer. This broad restriction, which includes chemically active substances which might be undesirable for the surrounding aquatic environment, is allowable because of the shielding effect of the outer polymer layer 98 over the inner polymer layer 99, which keeps any and all impregnated chemically active substances in the inner polymer layer 99 totally segregated and isolated from the surrounding aquatic environment, with no leakage or leaching of such substances into the surrounding water. Therefore, not only can environmentally safe chemically active substances be impregnated into the inner polymer layer 99, but those chemically active substances that would normally not be safe for exposure to the environment and surrounding water can also be impregnated in that layer with complete safety and freedom from aquatic environmental leakage.

These substances can include cupro-metallic substances of any form described herein, and currently available commercially available ship antifouling materials such as Tralopyril, Dichlorooctylisothiazolinone, DCOIT, 4/5-dichloro-2-noctly-4isothiazolin-3-one, Cybutryne, and so forth. Even tri-butyl-tin (TBT) can be used safely because it too will never touch the aquatic environment. While the most effective antifouling agent ever developed, TBT has been permanently banned in 2003 by the International Maritime Organization, and for political reasons, will never again be allowed to be used even as the multi-layer coatings described herein do make this chemical agent safe for the environment.

Many human and animal drugs that demonstrate an ability to eradicate bio-proliferative processes from biofouling animal organisms, such as the Ivermectin class of drugs, Lufenuron, tricyclic anti-depressants, Spinosad, and so forth, can be used in inner polymer 99. The broad spectrum of chemically active agents that can halt bio-proliferative processes caused by any undesirable plant, animal, bacterial, and fungal organisms may be used, as long as they are physically and chemically compatible with the polymer of the inner polymer layer and the other chemically active substances impregnated there.

The foregoing is to be understood as being in every respect illustrative and exemplary, but not restrictive, and the scope of the invention disclosed herein is not to be determined from the Detailed Description, but rather from the claims as interpreted according to the full breadth permitted by the patent laws. It is to be understood that the embodiments shown and described herein are only illustrative of the principles of the present invention and that those skilled in the art may implement various modifications without departing from the scope and spirit of the invention. Those skilled in the art could implement various other feature combinations without departing from the scope and spirit of the invention. 

The invention claimed is:
 1. A method of protecting a surface, comprising: applying an inner polymer layer onto a surface, the inner polymer layer being impregnated with a biologically active chemical substance that protects the surface from biofouling-induced chemical, biological, and bio-proliferative damage, the inner polymer layer being an epoxy polymer; and applying an outer polymer layer onto the inner polymer layer, the outer polymer layer being impregnated with a biologically active chemical substance that protects the inner polymer layer from biofouling-induced chemical, biological, and bio-proliferative damage and that repels biofouling animal organisms to prevent invasion of the inner polymer layer, wherein the outer polymer layer is selected from the group consisting of polyurethanes and fluorourethanes and wherein the biologically active chemical substance of the outer polymer layer includes a copper-zinc-tin alloy with zinc having a weight percentage between 8% and 12%, with tin having a weight percentage between 1% and 5%, and with copper having a weight percentage of at least 85% of the alloy.
 2. The method of claim 1, wherein the biologically active chemical substance of the outer polymer layer further includes at least one substance selected from the group consisting of zinc pyrithione, nonivamide, clonidine, methyldopa, oxymetazoline, octopamine, medetomidine, dexmedetomidine, any agonist of the human alpha2-adrenergic receptor, and any agonist of the non-human octopamine receptor.
 3. The method of claim 1, wherein the copper-zinc-tin alloy has a composition of about 90% copper, about 9% zinc, and about 1% tin.
 4. The method of claim 1, wherein the biologically active chemical substance of the inner polymer layer kills biofouling animal organisms that penetrate the outer polymer layer, to protect the surface.
 5. The method of claim 4, wherein the biologically active chemical substance of the inner polymer layer includes at least one substances selected from the group consisting of elemental copper, cupro-metallic alloys of copper, a copper-zinc-tin alloy, a powdered copper-zinc-tin alloy, powdered water-insoluble cuprous and cupric salts of copper, powdered water-soluble cuprous and cupric salts of copper, non-copper heavy metal oxides, dichloro-octyl-isothiazolinone and tralopyril, the ivermectin class of drug, Lufenuron, tricyclic anti-depressants, and Spinosad.
 6. A method of protecting a surface, comprising: applying a non-ablative inner polymer layer onto a surface, the inner polymer layer being impregnated with a biologically active chemical substance that protects the surface from biofouling-induced chemical, biological, and bio-proliferative damage, wherein the inner polymer layer is a flexible epoxy polymer; and applying a non-ablative outer polymer layer onto the inner polymer layer, the outer polymer layer being impregnated with a biologically active chemical substance combination that protects the inner polymer layer from biofouling-induced chemical, biological, and bio-proliferative damage by simultaneous repulsive effects on octopamine, GABA, and TRPV1 cell membrane receptors of biofouling animal organisms, wherein the outer polymer layer includes a material selected from the group consisting of polyurethanes and fluorourethanes and wherein the biologically active chemical substance combination of the outer polymer layer includes a copper-zinc-tin alloy with zinc having a weight percentage between 8% and 12%, with tin having a weight percentage between 1% and 5%, and with copper having a weight percentage of at least 85% of the alloy.
 7. The method of claim 6, wherein the non-ablative inner polymer layer protects the surface without discharge into surrounding water of the biologically active chemical substance.
 8. The method of claim 6, wherein the non-ablative outer polymer layer protects the non-ablative inner polymer layer without discharge into surrounding water of the biologically active chemical substance.
 9. The method of claim 6, wherein the biologically active substance of the non-ablative inner polymer layer comprises a cupro-metallic salt, and the biologically active chemical substance combination of the non-ablative outer polymer layer further comprises zinc pyrithione, wherein the non-ablative outer polymer layer prevents the cupro-metallic salt from converting the zinc pyrithione to copper pyrithione in the outer polymer layer.
 10. The method of claim 6, wherein the non-ablative outer polymer layer encases the non-ablative inner polymer layer, so that there is no exposure of anti-biofouling substances within the non-ablative inner polymer layer to a surrounding environment.
 11. The method of claim 6, further comprising applying an inner primer layer on the surface before applying the non-ablative inner polymer layer, the inner primer layer being formed from the flexible epoxy polymer, without the biologically active chemical substance of the inner polymer layer, to prevent incompatibility between the biologically active chemical substance and a material of the surface.
 12. The method of claim 6, further comprising applying an outer primer layer on the non-ablative inner polymer layer, before applying the non-ablative outer polymer layer, the outer primer layer being formed from the flexible epoxy polymer, without the biologically active chemical substance of the inner polymer layer, to prevent incompatibility between the biologically active chemical substance of the inner polymer layer with the biologically active chemical substance of the outer polymer layer.
 13. A method of protecting a surface, comprising: applying a non-ablative inner polymer layer onto a surface, the inner polymer layer being impregnated with a biologically active chemical substance that protects the surface from biofouling-induced chemical, biological, and bio-proliferative damage, wherein the inner polymer layer is a flexible epoxy polymer; and applying a non-ablative outer polymer layer onto the inner polymer layer, the outer polymer layer being impregnated with a powdered copper-zinc-tin alloy that remains chemically intact in contact with the surrounding water, wherein the outer polymer layer is selected from the group consisting of polyurethanes and fluorourethanes and wherein copper-zinc-tin alloy includes zinc having a weigh percentage between 8% and 12%, with tin having a weight percentage between 1% and 5%, and with copper having a weight percentage of at least 85% of the alloy.
 14. The method of claim 13, wherein the copper-zinc-tin alloy has a composition of about 90% copper, about 9% zinc, and about 1% tin.
 15. The method of claim 13, wherein the outer polymer layer further includes a biologically active chemical substance selected from the group consisting of zinc pyrithione, copper pyrithione, nonivamide, clonidine, methyldopa, oxymetazoline, octopamine, medetomidine, dexmedetomidine, any agonist of the human alpha2-adrenergic receptor, and any agonist of the non-human octopamine receptor.
 16. The method of claim 13, wherein the biologically active chemical substance of the inner polymer layer includes one or more substances selected from the group consisting of elemental copper, cupro-metallic alloys of copper, a copper-zinc-tin alloy, a powdered copper-zinc-tin alloy, powdered water-insoluble cuprous and cupric salts of copper, powdered water-soluble cuprous and cupric salts of copper, non-copper heavy metal oxides, dichloro-octyl-isothiazolinone and tralopyril, the Ivermectin class of drugs, Lufenuron, tricyclic anti-depressants, and Spinosad.
 17. The method of claim 13, wherein the non-ablative outer polymer layer encases the non-ablative inner polymer layer, so that there is no exposure of substances within the non-ablative inner polymer layer to a surrounding environment. 